Compositions and methods for modifying a surface suited for semiconductor fabrication

ABSTRACT

The disclosure pertains to compositions and methods for modifying or refining the surface of a wafer suited for semiconductor fabrication. The compositions include working liquids useful in modifying a surface of a wafer suited for fabrication of a semiconductor device. In some embodiments, the working liquids are aqueous solutions of initial components substantially free of loose abrasive particles, the components including water, a surfactant, and a pH buffer exhibiting at least one pK a  greater than 7. In certain embodiments, the pH buffer includes a basic pH adjusting agent and an acidic complexing agent, and the working liquid exhibits a pH from about 7 to about 12. In further embodiments, the disclosure provides a fixed abrasive article comprising a surfactant suitable for modifying the surface of a wafer, and a method of making the fixed abrasive article. Additional embodiments describe methods that may be used to modify a wafer surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.09/707,269, filed Nov. 6, 2000, now pending; which is a continuation ofU.S. application Ser. No. 09/091,932, issued as U.S. Pat. No. 6,194,317,which is a 35 USC §371 national stage application of InternationalApplication No. PCT/US98/08693, which is a continuation-in-part of U.S.application Ser. No. 08/846,726 filed Apr. 30, 1997, abandoned, thedisclosure of which is incorporated by reference in their entiretyherein.

BACKGROUND

This disclosure relates generally to a method of modifying exposedsurfaces of wafers suited for semiconductor fabrication and particularlyto a method of modifying exposed surfaces of structured wafers suitedfor semiconductor fabrication using an abrasive article.

During integrated circuit manufacture, semiconductor wafers used insemiconductor fabrication typically undergo numerous processing steps,including deposition, patterning, and etching steps. Details of thesemanufacturing steps for semiconductor wafers are reported by Tonshoff etal., “Abrasive Machining of Silicon”, published in the Annals of theInternational Institution for Production Engineering Research, (Volume39/2/1990), pp. 621-635. In each manufacturing step, it is oftennecessary or desirable to modify or refine an exposed surface of thewafer in order to prepare the wafer for subsequent fabrication ormanufacturing steps.

For example, after a deposition step, the deposited material or layer ona wafer surface generally needs further processing before additionaldeposition or subsequent processing occurs. In another example, after anetching step, there is often a need to deposit either, or both,conducting or insulating materials in layers on the etched surface areasof a wafer. A specific example of this process is used in metalDamascene processes.

In the Damascene process, a pattern is etched into an oxide dielectriclayer. After etching, optional adhesion/barrier layers are depositedover the entire surface and then a metal is deposited over or on top ofthe adhesion/barrier layers. The deposited metal layer is then modified,refined or finished by removing the deposited metal and regions of theadhesion/barrier layer on the surface. Typically, enough surface metalis removed so that the outer exposed surface of the wafer comprises bothmetal and an oxide dielectric material. A top view of the exposed wafersurface would reveal a substantially planar surface with metalcorresponding to the etched pattern and dielectric material adjacent tothe metal. The metal(s) and oxide dielectric material(s) located on themodified surface of the wafer inherently have different physicalcharacteristics, such as different hardness values. An abrasive articleused to modify a wafer produced by the Damascene process must becarefully designed so as to simultaneously modify the materials withoutscratching the surface of either material. Further, the abrasive articlemust be able to create a substantially planar outer exposed surface on awafer having an exposed area of a metal and an exposed area of adielectric material.

Such a process of modifying the deposited metal layer until the oxidedielectric material is exposed on the wafer outer surface leaves littlemargin for error because of the submicron dimensions of the metalfeatures located on the wafer surface. It is clear that the removal rateof the deposited metal must be fast to minimize manufacturing costs.Further, metal removal from areas which were not etched must becomplete. Still further, metal remaining in etched areas must be limitedto discrete areas or zones. Yet further, the remaining metal must becontinuous within an area or zone to ensure proper conductivity. Inshort, the metal modification process must be uniform, controlled, andreproducible on a submicron scale.

Furthermore, as a method for isolating elements of a semiconductordevice, a great deal of attention has recently been directed towards ashallow trench isolation (STI) process where a silicon nitride layer isformed on a silicon substrate, shallow trenches are formed via etchingor photolithography, and a dielectric layer is deposited to fill thetrenches. Due to variation in the depth of trenches, or lines, formed inthis manner, it is typically necessary to deposit an excess ofdielectric material on top of the substrate to ensure complete fillingof all trenches.

The excess dielectric material (e.g., an oxide) is then typicallyremoved by a chemical-mechanical planarization process to expose thesilicon nitride layer. In order to achieve a highly planar surface, theheight of the nitride layer and the remaining trench oxide layer, shouldbe substantially the same. Generally, past practice has been toemphasize selectivity for oxide polishing in preference to siliconnitride polishing. Thus, the silicon nitride layer has served as astopping layer during the chemical-mechanical planarization process, asthe overall polishing rate has decreased upon exposure of the siliconnitride layer.

Compositions and methods for planarizing or polishing the surface of asubstrate are well known in the art. One conventional method ofmodifying or refining exposed surfaces of wafers employs methods thattreat a wafer surface with a slurry containing a plurality of looseabrasive particles dispersed in a liquid. Typically this slurry isapplied to a polishing pad and the wafer surface is then ground or movedagainst the pad in order to remove or take off material on the wafersurface. Generally, the slurry also contains agents which chemicallyreact with the wafer surface. This type of process is commonly referredto as a chemical-mechanical planarization (CMP) process.

One problem with CMP slurries, however, is that the process must becarefully monitored in order to achieve a desired wafer surfacetopography. A second problem is the mess associated with loose abrasiveslurries. Another problem is that the slurries generate a large numberof particles which must be removed from the surface of the wafer anddisposed of following wafer treatment. Handling and disposal of theseslurries generates additional processing costs for the semiconductorwafer fabricator.

An alternative to CMP slurry methods uses an abrasive article to modifyor refine a semiconductor surface. This alternative CMP process isreported in International Publication No. WO 97/11484, published Mar.27, 1997. The reported abrasive article has a textured abrasive surfacewhich includes abrasive particles dispersed in a binder. In use, theabrasive article is contacted with a semiconductor wafer surface, oftenin the presence of a fluid or liquid, with a motion adapted to modify asingle layer of material on the wafer and provide a substantiallyplanar, uniform wafer surface. Use of an abrasive article overcomes asignificant number of problems associated with CMP slurries.

Embodiments of the present disclosure exploit the advantages afforded byuse of abrasive articles to modify surfaces of semiconductor wafers inorder to expose at least two different materials, typically havingdifferent hardness values on the surface of a wafer.

SUMMARY

This disclosure pertains to methods of modifying or refining the surfaceof a wafer suited for semiconductor fabrication. For example, oneexemplary method may be used to modify a wafer having a first materialhaving a surface etched to form a pattern or a design and a secondmaterial deployed over the surface of the first material. A first stepof this method comprises contacting the second material of the wafer toa plurality of three-dimensional abrasive composites fixed to anabrasive article, the three-dimensional abrasive composites comprising aplurality of abrasive particles fixed and dispersed in a binder. Asecond step is relatively moving the wafer while the second material isin contact with the plurality of abrasive composites until the exposedsurface of the wafer is substantially planar and comprises at least onearea of exposed first material and one area of exposed second material.The second material is typically a metal, however the second materialmay be an intermediate material such as an adhesion/barrier layer, or acombination of a metal and an adhesion/barrier layer. The first materialis typically a dielectric material. Suitable intermediate materials oradhesion/barrier layers include metals, oxides, nitrides, and silicides.Some particularly suitable intermediate materials or adhesion/barrierlayers include tantalum, titanium, tantalum nitride, titanium nitride,and silicon nitride.

In another exemplary method of modifying the surface of a wafer, a firstdielectric barrier material may be deployed over a patterned wafersurface, and a second dielectric material may deployed over the surfaceof the first dielectric barrier material. A first step of this methodcomprises contacting the second dielectric material of the wafer to aplurality of three-dimensional abrasive composites fixed to an abrasivearticle, the three-dimensional abrasive composites comprising aplurality of abrasive particles fixed and dispersed in a binder. Asecond step is relatively moving the wafer while the second dielectricmaterial is in contact with the plurality of abrasive composites untilthe exposed surface of the wafer is substantially planar and comprisesat least one area of exposed first dielectric barrier material and onearea of exposed second dielectric material. The second dielectricmaterial is typically silicon oxide, for example, silicon dioxide. Thefirst dielectric barrier material is typically silicon nitride.

As used in this specification, wafer typically includes a first materialwith a surface etched to form a pattern or a design and a secondmaterial deployed over the surface of the first material. The designsassociated with the first material include patterned areas, groovedareas, and vias, as well as other structures which make up a completedsemiconductor device. The wafer surface produced by a process such asthe Damascene process, and modified by the abrasive article of thepresent disclosure, is preferably free of scratches or other defectsthat would interfere with the function of the semiconductor device. Inpreferred embodiments, the wafer surface is substantially planar and hasa surface free of scratches or other defects as measured by an Rt value.Preferred Rt values provided by certain embodiments of this disclosureare typically less than about 3,000 Angstroms, preferable less thanabout 1,000 Angstroms, and most preferable less than about 500Angstroms. The wafer may include a third, fourth, fifth, or morematerials forming layers on a base layer of the wafer. Each layer may bemodified as exemplified above for a wafer having only a first materialand a second material.

A method of modifying a wafer during the Damascene process may, forexample, start with a wafer having at least a first material and asecond material present on the base of the wafer. At least one of thematerials may have a surface etched to form a design. An outer materialis deployed over the first and second materials so as to fill the designetched into the surface. The wafer is placed in contact with a pluralityof three-dimensional abrasive composites fixed to an abrasive article.The outer material of the wafer is placed in contact with a plurality ofthree-dimensional abrasive composites fixed to an abrasive article, theabrasive composite comprising a plurality of abrasive particles fixedand dispersed in a binder. The wafer is moved relative to the abrasivearticle while the outer material is in contact with the plurality ofabrasive composites until the exposed surface of the wafer issubstantially planar and comprises at least one area of exposed firstmaterial and one area of exposed second material.

In one embodiment of this disclosure, a method of modifying a wafer maybegin with a layer comprised of conductive material deployed over atleast one dielectric material. The dielectric material having a surfaceetched to form a design. Such a wafer may be modified by contacting andrelatively moving the exposed major surface of the wafer (conductivematerial) with respect to the abrasive article. The abrasive articletypically comprises an exposed major surface of a plurality of textured,three-dimensional abrasive composite comprising a plurality of abrasiveparticles fixed and dispersed in a binder. Contact and motion ismaintained between the plurality of abrasive composites of the abrasivearticle and the conductive material until an exposed surface of thewafer is substantially planar and comprises at least one area of exposedconductive material and at least one area of exposed dielectricmaterial, and the exposed surfaces of conductive material and theexposed surfaces of dielectric material lies in a single plane. Thedielectric material may be covered by one or more intermediate materialssuch as an adhesion/barrier layer. Typically, the exposed dielectricmaterial surface is essentially free of the intermediate material afterremoval of the conductive material. Alternatively, removal of theconductive material may expose only the surface of the intermediatematerial and the conductive material. Continued modification may thenexpose on the surface of the wafer the dielectric material and theconductive material.

The present method is particularly adapted to modify conductivesurfaces, typically referred to as the second material in the presentapplication. The conductive surfaces may be made from a variety ofconductive materials having resistivity values of less than about 0.1ohm-cm. Preferred conductive materials include metals such as tungsten,copper, aluminum, aluminum copper alloy, gold, silver, or various alloysof these metals. Preferred dielectric materials generally havedielectric constants less than about 5.

In another exemplary embodiment of this disclosure, a CMP method isprovided for modifying a surface of a substrate such as a semiconductorwafer to remove a selective thickness portion thereof. In one particularexemplary embodiment, the method comprises:

a. providing a wafer comprising at least a first material having asurface etched to form a pattern, a second material deployed over atleast a portion of the surface of the first material, and a thirdmaterial deployed over at least a portion of the surface of the secondmaterial;

b. contacting the third material of the wafer, in the presence of anaqueous working liquid substantially free of loose abrasive particlesand including water, a pH buffer exhibiting at least one pK_(a) greaterthan 7, and a surfactant, the pH buffer including a basic pH adjustingagent and an acidic complexing agent, and the working liquid exhibitinga pH from about 7 to about 12, with a plurality of three-dimensionalabrasive composites fixed to an abrasive article, the three-dimensionalabrasive composites comprising a plurality of abrasive particles fixedand dispersed in a binder; and

c. relatively moving the wafer while the third material is in contactwith the plurality of abrasive composites until an exposed surface ofthe wafer is substantially substantially planar and comprises at leastone area of exposed third material and one area of exposed secondmaterial.

In a further exemplary embodiment of a CMP STI method, the methodcomprises:

a) providing a wafer comprising at least a barrier material deployedover at least a portion of the wafer; and a dielectric material deployedover at least a portion of the surface of the barrier material;

b) contacting the dielectric material of the wafer, in the presence ofan aqueous working liquid substantially free of loose abrasive particlesand including water, a pH buffer exhibiting at least one pK_(a) greaterthan 7, and a surfactant, the pH buffer including a basic pH adjustingagent and an acidic complexing agent, and the working liquid exhibitinga pH from about 7 to about 12, with a plurality of three-dimensionalabrasive composites fixed to an abrasive article, the three-dimensionalabrasive composites comprising a plurality of abrasive particles fixedand dispersed in a binder; and

c) relatively moving the wafer while the dielectric material is incontact with the plurality of abrasive composites until an exposedsurface of the wafer is substantially planar and comprises at least onearea of exposed dielectric material and one area of exposed barriermaterial.

In one particular exemplary embodiment, the dielectric materialcomprises silicon oxide, and the barrier material comprises siliconnitride.

In certain exemplary methods, the movement between the wafer andabrasive article occurs under pressure in a range of about 0.1 to 25pounds per square inch (psi), about to about kilo-Pascals (kPa),preferably under a pressure in a range of about 0.2 to 15 psi (about1.38 to about 103.42 kPa). In another embodiment of this disclosure, thewafer and abrasive article are rotated and/or moved against each other.For example, either the abrasive article or the wafer or both theabrasive article and the wafer are rotated relative to the other as wellas being moved linearly along relative centers of the wafer and abrasivearticle. The wafer and the abrasive article may also be moved in anelliptical or a figure eight type pattern as the speed varies along thepath. The rotational motion or speed of rotation between the wafer andabrasive article may be between 1 rpm to 10,000 rpm. Preferredrotational speeds for the abrasive article are when the abrasive articlerotates at a speed between 10 rpm to 1,000 rpm, and more preferablybetween 10 rpm to 250 rpm and more preferably between 10 rpm to 60 rpm.Preferred rotational speeds for the wafer are when the wafer rotates ata speed between 2 rpm to 1,000 rpm, more preferable between 5 rpm to 500rpm, and still more preferred between 10 rpm to 100 rpm.

In a further embodiment of this disclosure, the conductive surface ofthe wafer is modified by the abrasive article in the presence of aworking liquid. One useful working liquid is an aqueous solution thatincludes a variety of different additives. Suitable additives include pHadjusting agents (e.g. acids or bases), as well as complexing,oxidizing, or passivating agents, surfactants, wetting agents, buffers,rust inhibitors, lubricants, soaps, or combinations of these additives.Additives may also include agents which are reactive with the secondmaterial, e.g., metal or metal alloy conductors on the wafer surfacesuch as oxidizing, reducing, passivating, or complexing agents. Examplesof oxidizing agents include hydrogen peroxide, nitric acid, potassiumferricyanide, ferric nitrate, or combinations of these agents. Examplesof complexing agents include ammonium hydroxide and ammonium carbonate.Further, the working liquid may be relatively free of additives or otheragents. In this embodiment, the working liquid may be tap water,distilled water, or deionized water. A suitable passivating agent isbenzotriazole.

In one exemplary embodiment of a working liquid useful in modifying asurface of a wafer suited for fabrication of a semiconductor device, theworking liquid comprises an aqueous solution of initial componentssubstantially free of loose abrasive particles, the components includingwater, a pH buffer exhibiting at least one pK_(a) greater than 7, and asurfactant, the pH buffer comprising a basic pH adjusting agent and anacidic complexing agent, and the working liquid exhibiting a pH fromabout 7 to about 12. In certain featured embodiments, the working liquidcomprises a fluorochemical surfactant, and the working liquid exhibits apH from about 7 to about 11.

In another exemplary embodiment, the disclosure provides a fixedabrasive article comprising a surfactant suitable for chemicalmechanical polishing of a surface of a substrate. In certain exemplaryembodiments, a method of preparing a fixed abrasive article comprising asurfactant suitable for modifying a surface of a wafer in a chemicalmechanical polishing process comprises:

a. providing a fixed abrasive article having a surface comprising aplurality of three-dimensional abrasive composites fixed to an abrasivearticle, the three-dimensional abrasive composites comprising aplurality of abrasive particles fixed and dispersed in a binder;

b. exposing the surface to a surfactant solution in a solvent;

c. drying the fixed abrasive article to remove at least a portion of thesolvent, thereby forming a coating of surfactant on at least a portionof the surface.

Optionally, steps (a)-(c) may be repeated at a polishing rate until atarget polishing rate is obtained, and the polishing rate thereafterremains within about 200 Å/min of the target polishing rate, when thefixed abrasive article is used to polish a plurality of wafer surfaces.In some exemplary embodiments, the solvent may be an aqueous solvent(e.g. water), a nonaqueous solvent (e.g. an alcohol or other organicsolvent), or a mixture of an aqueous and a nonaqueous solvent (e.g.ethanol and water).

The preferred fixed abrasive article for some embodiments of the presentmethod comprises a textured, three-dimensional abrasive outer surfacemade of a plurality of abrasive particles dispersed in a binder. It ispreferred that the abrasive article further comprises a backing and morepreferably this backing is a polymeric film. This backing will have afront surface and a back surface. The backing may be selected from agroup of materials which have been used for abrasive articles such aspaper, nonwovens, cloth, treated cloth, polymeric film, and primedpolymeric film. In a preferred embodiment, the backing is a primedpolyester film.

At least one surface of the backing is coated with a binder and abrasiveparticles. It is preferred that the abrasive coating is somewhaterodible. Suitable binders may be organic or inorganic materials. It ispreferred that the binder is an organic binder. Further, the binder maybe a thermoplastic binder or thermosetting binder. If the binder is athermosetting binder, the binder may preferably be formed from a binderprecursor. Specifically, suitable binder precursors are in an uncured,flowable state. When the abrasive article is made, the binder precursoris exposed to conditions (typically an energy source) to help initiatecure or polymerization of the binder precursor. During thispolymerization or curing step, the binder precursor is solidified andconverted into a binder. In certain embodiments of this disclosure, itis preferred that the binder precursor comprises a free radical curablepolymer. Upon exposure to an energy source, such as radiation energy,the free radical curable polymer is crosslinked to form the binder.Examples of some preferred free radical curable polymers includeacrylate monomers, acrylate oligomers or acrylate monomer and oligomercombinations. Preferred binder precursors include acrylate functionalurethane polymers.

The abrasive particles can be any suitable abrasive particles thatprovide the desired properties on the exposed wafer surface and specificabrasive particles may be used for specific types of materials. Desiredproperties may include metal cut rate, surface finish, and planarity ofthe exposed wafer surface. The abrasive particles may be selecteddepending upon the specific material of the wafer surface. For examplefor copper wafer surfaces, the preferred abrasive particles includealpha alumina particles. Alternatively for aluminum wafer surfaces, thepreferred abrasive particles include alpha and chi alumina.

The size of the abrasive particles depends in part upon the particularcomposition of the abrasive article and selection of the working liquidused during the process. In general, suitable abrasive particles havingan average particle size no greater than about 5 micrometers arepreferred. Even more preferred are abrasive articles in which theaverage abrasive particle size is no greater than one micrometer and,particularly, no greater than about 0.5 micrometer.

The abrasive particles may be used in combination with filler particles.Examples of preferred filler particles include magnesium silicate,aluminum trihydrate, and combinations thereof.

In certain embodiments of the disclosure, the binder and abrasiveparticles provide a plurality of shaped abrasive composites. Abrasivecomposite features may comprise a variety of three-dimensional shapesincluding those bounded by a first closed plane curve extended into thethird dimension with positive, zero, or negative taper to a secondclosed plane curve substantially parallel to the first plane curve andto the backing, or to a point. The first and second plane curves, andany intermediate, transitional curves, need not be everywhere convex.The second closed plane figure may be either larger or smaller than thefirst closed plane figure, may be noncongruent with the first planefigure, or may be rotated with respect to the first closed plane curve.The axis of extension, defined by the trajectory of the centroid of theclosed plane curve need not be perpendicular to the first plane. Thesecond closed plane curve may less preferably be tilted with respect tothe first closed plane curve. Smaller scale features, such as grooves,may be formed on the distal surface of the abrasive composite feature.

A suitable composite feature might have, for example, a circular crosssection at the base which is transformed smoothly, or in one or morediscrete steps, to a six-pointed, non-equant star of slightly smallerequivalent diameter at the distal plane. These abrasive composites maybe both either precisely shaped or irregularly shaped. The abrasivecomposites are preferably spaced apart from each other. Preferredabrasive composites have a geometric shape such as frustums of spheres,pyramids, truncated pyramids, cones, cubes, blocks, rods, cross orpost-like with flat topped surfaces. The abrasive composites typicallyare arranged in a specific order or pattern on a surface of the backing.Alternatively, the abrasive composites may also be randomly arranged ona surface of the backing. The abrasive article may also consist of long,continuous rows of the abrasive composites. A range of areal densitiesof the abrasive composites may be used in the abrasive article. Suitableareal density ranges are at least 2 abrasive composites per squarecentimeter to at least 1,000 abrasive composites per square centimeter.In addition, the size of the abrasive composites may include heights ofless than 2 millimeters, less than 0.5 millimeter, or less than 0.1millimeter.

Still further, the abrasive composites may also include one or moreadditives. Suitable additives include abrasive particle surfacemodification additives, coupling agents, fillers, expanding agents,fibers, antistatic agents, initiators, suspending agents, lubricants,wetting agents, surfactants, pigments, dyes, UV stabilizers, complexingagents, chain transfer agents, accelerators, catalysts, activators,passivating agents, or combinations of these additives.

Additionally, the abrasive coating may be secured to a subpad. Thesubpad will have a front surface and a back surface and the abrasivecoating will be present over the front surface of the support pad. Apressure sensitive adhesive may be applied on the back surface of thebacking of the abrasive article in order to fix the abrasive article tothe subpad.

The above summary is not intended to describe each illustratedembodiment or every implementation of the present disclosure. TheDrawings and the Detailed Description that follow more particularlyexemplify certain preferred embodiments using the principles disclosedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional view of a portion of a structuredwafer before surface modification;

FIG. 2 is a schematic cross sectional view of a portion of a structuredwafer after surface modification;

FIG. 3 is a partial side schematic view of one apparatus for modifyingthe surface of a wafer used in semiconductor fabrication;

FIG. 4 is a cross sectional view of a portion of an abrasive articleuseful in the process of the present disclosure;

FIG. 5 is a cross sectional view of a portion of another abrasivearticle useful in a process of the present disclosure;

FIG. 6 is a cross sectional view of a portion of an abrasive articleuseful in a process of the present disclosure; and

FIG. 7 is a top plan view of a portion of another abrasive articleuseful in a process of the present disclosure.

FIG. 8 is a plot of polishing rate as a function of the number of wafersprocessed according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

Throughout this application, the following definitions apply:

A “fixed” abrasive article is an integral abrasive article that issubstantially free of unattached abrasive particles except as may begenerated during the planarization process.

A “three-dimensional” abrasive article is an abrasive article havingnumerous abrasive particles extending throughout at least a portion ofits thickness such that removing some of the particles duringplanarization exposes additional abrasive particles capable ofperforming the planarization function.

A “textured” abrasive article is an abrasive article having raisedportions and recessed portions in which at least the raised portionscontain abrasive particles and binder.

An “erodible” abrasive article is an abrasive article that breaks downunder use conditions in a controlled manner.

An “abrasive agglomerate” refers to a plurality of abrasive particlesbonded together in the form of a unitary particulate mass.

An “abrasive composite” refers to one of a plurality of shaped bodieswhich collectively provide a textured, three-dimensional abrasivearticle comprising abrasive particles and a binder. The abrasiveparticles may be in the form of abrasive agglomerates.

A “precisely shaped abrasive composite” refers to an abrasive compositehaving a molded shape that is the inverse of the mold cavity which isretained after the composite has been removed from the mold. Preferably,the composite is substantially free of abrasive particles protrudingbeyond the exposed surface of the shape before the abrasive article hasbeen used, as described in U.S. Pat. No. 5,152,917 (Pieper et al.).

In conventional semiconductor device fabrication schemes, a flat, basesilicon wafer is subjected to a series of processing steps which deposituniform layers comprising regions of two or more discrete materialswhich together form a single layer of what will become a multilayerstructure. Although the individual elements within a given layer may beformed in a variety of ways, it is common to apply a uniform layer of afirst material to the wafer itself or to an existing layer of anintermediate construct by any of the means commonly employed in the art,to etch pits into or through that layer, and then to fill the pits witha second material. Alternatively, features of approximately uniformthickness comprising a first material may be deposited onto the wafer,or onto a previously fabricated layer of the wafer, usually through amask, and then the regions adjacent to those features may be filled witha second material to complete the layer. When completed, the outersurface is substantially globally planar and parallel to the basesilicon wafer surface.

Known filling operations are usually accomplished by depositing acoating of the second material onto the exposed surface of theintermediate wafer, which coating is of sufficient thickness to fillthose portions of the layer under construction which have been leftunoccupied by the previous deposition/etching or masked deposition stepor steps. As a result, the regions of the layer which will comprise thefirst material in the finished semiconductor device will also be coveredby the second material and the total thickness of the first materialplus the overlying second material will be greater than the desiredthickness of the finished exposed layer in the wafer. In the creation ofa multilayer metalization architecture using a Damascene process on theexposed surface of the wafer being processed, grooves or pits arepatterned on a dielectric first material, e.g., silicon dioxide. Theouter most surfaces of the remaining dielectric first material and anyoverlying adhesion/barrier layers define a globally substantially planarfirst surface which locally bridges the grooves or pits withoutdeparting from planarity. A second globally substantially planar surfaceis defined by the aggregate bottoms of the grooves or pits similarlybridged locally for the purpose of the definition so as to pass throughthe patterned dielectric without interruption. Both the first and secondsubstantially globally planar surfaces are preferably parallel to theoriginal silicon wafer surfaces and to the surface of any layers of thedevice which may lie immediately below the layer being fabricated. Thesecond substantially globally planar surface will often correspond tothe surface of an immediately underlying layer if it is present.Optional adhesion/barrier layers, e.g., titanium nitride or titanium,and subsequent metal second material, e.g., copper or aluminum, layersare conformally deposited into any etched or pattern areas of the wafer.The exposed outer surface of the intermediate wafer will often then liecompletely above the first substantially globally planar surface asdefined herein.

Previously, the excess second material commonly has been removed byglobal chemical mechanical planarization (CMP) utilizing an abrasiveslurry and a polishing pad. Certain embodiments of the currentdisclosure replace the messy slurry CMP with a relatively cleanplanarization process which employs a three-dimensional shaped abrasivearticle wherein the structured elements of the abrasive article comprisea plurality of abrasive grains within a binder. A working fluidcomprising ingredients which chemically modify the second material orwhich otherwise facilitate the removal of the second material from thesurface of the intermediate wafer under the action of the abrasivearticle may be used in conjunction with the abrasive article.

The following non-limiting, description exemplifies the various methodsof certain embodiments of this disclosure. Delineation of the metallines, pads, and vias formed by the Damascene process is finallyobtained by a global planarization process which employs athree-dimensional abrasive article. The planarization process isaccomplished by contacting the exposed faces of the wafer to beplanarized to a plurality of abrasive composites on the surface of anabrasive article of the present disclosure, and relatively moving thewafer and the abrasive article while maintaining contact. A workingfluid may be used that comprises ingredients that chemically modify thesecond material or which otherwise facilitate the removal of the secondmaterial from the surface of a first wafer material under the action ofthe abrasive article. The planarization process is continued until theexposed outer surface of the wafer comprises at least one area ofexposed second material and one area of exposed first material definedherein. Failure to continue the planarization process sufficiently maylead to undesirable bridging of the dielectric by the conductivematerial. Continuing the planarization process too far beyond the firstsubstantially globally planar surface will incur a risk of cutting oneor more of the conductive lines. In specific cases, removal rate of thesecond material becomes slower or stops when the surface of the firstmaterial is exposed and the removal rate of the first material isdifferent than the removal rate of the second material. The abrasivearticles of the present disclosure are designed to produce asubstantially planar surface on wafers comprising more than one materialwith each material having different removal rates. The abrasive articlesof the present disclosure are designed to minimally scratch the surfaceof these materials during planarization.

The roles of the dielectric and the metal may be reversed; the first andsecond materials need not be limited to dielectrics and conductors,respectively, or even to at least one of dielectrics and conductors. Oneembodiment of the method of the present disclosure may begin with awafer having more than two materials within a single layer of thefinished semiconductor device; a material immediately underlying aparticular region of either the first material or the second material,the material may be the first material, the second material, a thirdmaterial, or a combination of materials; a second substantially globallyplanar surface defined with respect to the outermost aggregate set ofbottoms of the grooves or pits if two or more such sets exist atdiffering depths within a single layer; a surface in which the secondmaterial is not present at every point above the eventual planarizedsurface of the final fabricated layer prior to the initiation of theplanarization process of the method; and a base having a material otherthan silicon. FIG. 1 is a representative view of a patterned wafer 10suitable for use in the process according certain embodiments of thedisclosure. For clarity, known features such as doped regions, activedevices, epitaxial layers, carrier and field oxide layers have beenomitted. Wafer 10 has a base 11 and a plurality of topographicalfeatures, typically made from any appropriate material such as singlecrystal silicon, gallium arsenide, and other materials known in the art.A barrier or adhesion layer 13, typically titanium nitride or titanium,covers the base layer and base features. Other barrier layers mayinclude tantalum, tantalum nitride, or silicon nitride.

A metal conductor layer 14 covers the front surface of barrier layer 13and base features. A variety of metal or metal alloys may be used suchas aluminum, copper, aluminum copper alloy, tungsten, silver, or gold.The metal layer is typically applied by depositing a continuous layer ofthe metal on barrier layer 13. Excess metal is then removed to form thedesired pattern of metal interconnects 15 illustrated in FIG. 2. Metalremoval provides discrete metal interconnect surfaces 15 and discretefeature surfaces 16 which preferably provides a planar surface free ofscratches or other defects which would otherwise interfere with theoperability of the finished semiconductor device.

In an additional exemplary embodiment, a method is provided formodifying a surface of a substrate such as a semiconductor wafer, whichsurface includes the surface of an upper layer of a dielectric materialsuch as a dielectric oxide, e.g., silicon dioxide (SiO₂) overlying alower layer of a barrier material, e.g. silicon nitride (Si₃N₄), toremove substantially completely the upper layer and expose substantiallycompletely the lower layer of silicon nitride as a substantially intactlayer essentially without removing any portion of the lower layer ofsilicon nitride.

In one exemplary embodiment, the method comprises:

a. providing a wafer comprising at least a first material having asurface etched to form a pattern, a second material deployed over atleast a portion of the surface of the first material, and a thirdmaterial deployed over at least a portion of the surface of the secondmaterial;

b. contacting the third material of the wafer, in the presence of anaqueous working liquid substantially free of loose abrasive particlesand including water, a pH buffer exhibiting at least one pK_(a) greaterthan 7, and a surfactant, the pH buffer including a basic pH adjustingagent and an acidic complexing agent, and the working liquid exhibitinga pH from about 7 to about 12, with a plurality of three-dimensionalabrasive composites fixed to an abrasive article, the three-dimensionalabrasive composites comprising a plurality of abrasive particles fixedand dispersed in a binder; and

c. relatively moving the wafer while the third material is in contactwith the plurality of abrasive composites until an exposed surface ofthe wafer is substantially planar and comprises at least one area ofexposed third material and one area of exposed second material.

In another particular exemplary embodiment, the method comprises a CMPSTI method including:

a) providing a wafer comprising at least a conductive material having asurface etched to form a pattern, a barrier material deployed over atleast a portion of the surface of the conductive material, and adielectric material deployed over at least a portion of the surface ofthe barrier material;

b) contacting the dielectric material of the wafer, in the presence ofan aqueous working liquid substantially free of loose abrasive particlesand including water, a pH buffer exhibiting at least one pK_(a) greaterthan 7, and a surfactant, the pH buffer including a basic pH adjustingagent and an acidic complexing agent, and the working liquid exhibitinga pH from about 7 to about 12, with a plurality of three-dimensionalabrasive composites fixed to an abrasive article, the three-dimensionalabrasive composites comprising a plurality of abrasive particles fixedand dispersed in a binder; and

c) relatively moving the wafer while the dielectric material is incontact with the plurality of abrasive composites until an exposedsurface of the wafer is substantially planar and comprises at least onearea of exposed dielectric material and one area of exposed barriermaterial.

In one particular exemplary embodiment, the dielectric materialcomprises silicon oxide, and the barrier material comprises siliconnitride.

Apparatus

FIG. 3 schematically illustrates an apparatus for modifying wafersuseful in the process according to the disclosure. Numerous variationsof this machine and/or numerous other machines may be useful withcertain embodiments of this disclosure. This type of apparatus andnumerous variations and other types of apparatus are known in the artfor use with polishing pads and loose abrasive slurries. An example of asuitable, commercially available apparatus is a CMP (chemical mechanicalprocess) machine available from IPEC/WESTECH of Phoenix, Ariz.Alternative CMP machines are available from STRASBAUGH or SPEEDFAM.

Apparatus 30 comprises head unit 31 connected to a motor (not shown).Chuck 32 extends from head unit 31; an example of such a chuck is agimbal chuck. The design of chuck 32 preferably accommodates differentforces and pivots so that the abrasive article provides the desiredsurface finish and flatness on the wafer. However, the chuck may or maynot allow the wafer to pivot during planarization.

At the end of chuck 31 is wafer holder 33. Wafer holder 33 secures wafer34 to head unit 31 and also prevents the wafer from becoming dislodgedduring processing. The wafer holder is designed to accommodate the waferand may be, for example, circular, oval, rectangular, square, octagonal,hexagonal, or pentagonal.

In some instances, the wafer holder includes two parts, an optionalretaining ring and a wafer support pad. The retaining ring may be agenerally circular device that fits around the periphery of thesemiconductor wafer. The wafer support pad may be fabricated from one ormore elements, e.g., polyurethane foam.

Wafer holder 33 extends alongside of semiconductor wafer 34 at ringportion 35. The ring portion (which is optional) may be a separate pieceor may be integral with holder 33. In some instances, wafer holder 33will not extend beyond wafer 34 such that wafer holder 33 does not touchor contact abrasive article 42. In other instances, wafer holder 33 doesextend beyond wafer 34 such that the wafer holder does touch or contactthe abrasive composite, in which case the wafer holder may influence thecharacteristics of the abrasive composite. For example, wafer holder 33may “condition” the abrasive article and remove the outermost portion ofthe surface of the abrasive article during processing.

The wafer holder or retaining ring may be made out of any material thatwill allow the abrasive article to impart the desired degree ofmodification to the wafer. Examples of suitable materials includepolymeric materials.

The speed at which wafer holder 33 rotates will depend on the particularapparatus, processing conditions, abrasive article, and the desiredwafer modification criteria. In general, however, wafer holder 33rotates between about 2 to about 1,000 rpm, typically between about 5 toabout 500 rpm, preferably between about 10 to about 300 rpm and morepreferably between about 20 to about 100 rpm. If the wafer holderrotates too slowly or too fast, then the desired cut rate may not beachieved.

Wafer holder 33 and/or base 42 may rotate in a circular fashion, spiralfashion, a non-uniform manner, elliptical fashion as a figure eight or arandom motion fashion. The wafer holder or base may also oscillate orvibrate, such as by transmitting ultrasonic vibrations through theholder or base.

The abrasive article for use with the currently employed 100 to 500 mmdiameter wafers will typically have a diameter between about 10 to 200mm, preferably between about 20 to 150 mm, more preferably between about25 to 100 mm. The abrasive article may rotate between about 5 to 10,000rpm, typically between about 10 to 1,000, between about 10 to 250 rpmand preferably between 10 rpm to 60 rpm. It is preferred that both thewafer and the abrasive article rotate in the same direction. However,the wafer and the abrasive article may also rotate in oppositedirections.

The interface between the wafer surface 34 and wafer holder 33preferably should be relatively flat and uniform to ensure that thedesired degree of planarization is achieved. Reservoir 37 holds workingliquid 39 (described in more detail below) which is pumped throughtubing 38 into the interface between wafer surface and abrasive article41 which is attached to base 42. It is preferred that duringplanarization there be a consistent flow of the working liquid to theinterface between the abrasive article and the wafer surface. The liquidflow rate will depend in part upon the desired planarization criteria(cut rate, surface finish and planarity), the particular waferconstruction and the exposed metal chemistry. The liquid flow ratetypically ranges from about 10 to 1,000 milliliters/minute, preferably10 to 500 milliliters/minute, and between about 25 to 250milliliters/minute.

During the modifying process of the disclosure, the abrasive article istypically secured to subpad 43 which acts as a support pad for theabrasive article. In part, the subpad provides both rigidity to allowthe abrasive article to effectively cut the exposed wafer surface andconformability such that the abrasive article will uniformly conform tothe exposed wafer surface. This conformability is important to achieve adesired surface finish across the entire exposed wafer surface. Thus,the choice of the particular subpad (i.e., the physical properties ofthe subpad) should correspond to the abrasive article such that theabrasive article provides the desired wafer surface characteristics (cutrate, surface finish and planarity).

Suitable subpads may be made from any desired material such as metal orpolymeric foam, rubber, and plastic sheeting and the subpad may be acomposite material. A preferred two component laminate subpad having aresilient polycarbonate layer and a conformable polyurethane foam layeris reported in U.S. Pat. No. 5,692,950.

The means used to attach the abrasive article to the subpad preferablyholds the abrasive article flat and rigid during planarization. Thepreferred attachment means is a pressure sensitive adhesive (e.g., inthe form of a film or tape). Pressure sensitive adhesives suitable forthis purpose include those based on latex crepe, rosin, acrylic polymersand copolymers (e.g., polybutylacrylate and other polyacrylate esters),vinyl ethers (e.g., polyvinyl n-butyl ether), alkyd adhesives, rubberadhesives (e.g., natural rubber, synthetic rubber, chlorinated rubber),and mixtures thereof. The pressure sensitive adhesive is preferablylaminated or coated onto the back side of the abrasive article usingconventional techniques. Another type of pressure sensitive adhesivecoating is further illustrated in U.S. Pat. No. 5,141,790.

The abrasive article may also be secured to the subpad using a hook andloop type attachment system. The loop fabric may be on the back side ofthe abrasive article and the hooks on the subpad. Alternatively, thehooks may be on the back side of the abrasive article and the loops onthe subpad. Hook and loop type attachment systems are reported in U.S.Pat. Nos. 4,609,581; 5,254,194; 5,505,747; and PCT WO 95/19242. The useof a vacuum platen has been disclosed in U.S. Pat. No. 5,593,344.

The process or method of the present disclosure may be modified tooptimize wafer modification. The abrasive article may include an opticalwindow or opening that allows an operator to look through the abrasivearticle and view the wafer adjacent the layer forming a plurality ofabrasive composites. In addition, conventional end-point detectionmethods that allow monitoring of the wafer polishing process, such asdetecting varying electrical characteristics of the substrate, varyingmechanical torque or drag, or varying the noises generated duringplanarization, may be used to optimize the present method of thedisclosure using abrasive articles comprising a plurality ofthree-dimensional abrasive composites. Methods which rely upon analysisof the effluent from the polishing operation are also expected to workwell with the fixed abrasive article. The absence of a large quantity offree abrasive particles in the effluent is expected to simplify suchanalysis and possibly enhance the overall effectiveness of such methods.Such methods are discussed in EP 824995 A and U.S. Pat. Nos. Re. 34,425;5,036,015; 5,069,002; 5,222,329; 5,244,534; 4,793,895; 5,242,524;5,234,868; 5,605,760; and 5,439,551.

Methods directed toward producing uniform wear rates across the surfaceof the object being polished and or across the surface of the polishingpad as discussed in U.S. Pat. Nos. 5,20,283; 5,177,908; 5,234,867;5,297,364; 5,486,129; 5,230,184; 5,245,790; and 5,562,530, may beadapted for use with the abrasive articles of the present disclosure.Conventional structures of the wafer carrier and the wafersupport/attachment means which do not inherently depend on a particularabrasive surface may be used with the textured, three-dimensionalabrasive composites of this disclosure. Although the abrasive surface ofa textured, three-dimensional abrasive composite does not generallyrequire routine conditioning, which is often employed with slurry/padcombinations, it may advantageously be conditioned or dressed to providea modified, superior initial surface or to remove accumulated depositsduring or between use by any suitable pad conditioning method known inthe art. Variations of the wafer planarization process which employeither a continuous belt or a supply roll of sheet pad material inconjunction with a slurry may also be employed by substituting a belt orroll of textured, three-dimensional abrasive composite and anappropriate working fluid, as described in U.S. Pat. No. 5,593,344.Polishing related art such as the structure of the wafer carrier and thewafer support/attachment means which do not inherently depend on aninteraction with a particular abrasive surface may be used with theabrasive article comprising textured, three-dimensional abrasivecomposites of this disclosure.

Operating Conditions

Variables which affect the wafer processing include the selection of theappropriate contact pressure between the wafer surface and abrasivearticle, type of liquid medium, relative speed and relative motionbetween the wafer surface and the abrasive article, and the flow rate ofthe liquid medium. These variables are interdependent, and are selectedbased upon the individual wafer surface being processed.

In general, since there can be numerous process steps for a singlesemiconductor wafer, the semiconductor fabrication industry expects thatthe process will provide a relatively high removal rate of material. Thematerial cut rate should be at least 100 Angstroms per minute,preferably at least 500 Angstroms per minute, more preferably at least1,000 Angstroms per minute, and most preferably at least 1500 Angstromsper minute. In some instances, it may be desirable for the cut rate tobe as high as at least 2,000 Angstroms per minute, and even 3,000 or4,000 Angstroms per minute. The cut rate of the abrasive article mayvary depending upon the machine conditions and the type of wafer surfacebeing processed.

However, although it is generally desirable to have a high cut rate, thecut rate must be selected such that it does not compromise the desiredsurface finish and/or topography of the wafer surface.

The surface finish of the wafer may be evaluated by known methods. Onepreferred method is to measure the Rt value of the wafer surface whichprovides a measure of “roughness” and may indicate scratches or othersurface defects. See, for example, Chapter 2, RST PLUS TechnicalReference Manual, Wyko Corp., Tucson, Ariz. The wafer surface ispreferably modified to yield an Rt value of no greater than about 4,000Angstroms, more preferably no greater than about 2,000 Angstroms, andeven more preferably no greater than about 500 Angstroms.

Rt is typically measured using an interferometer such as a Wyko RST PLUSInterferometer, purchased from Wyko Corp., or a TENCOR profilometer.Scratch detection may also be measured by dark field microscopy. Scratchdepths may be measured by atomic force microscopy. Scratch and defectfree surfaces are highly desirable.

The interface pressure between the abrasive article and wafer surface(i.e., the contact pressure) is typically less than about 30 psi (about206.84 kPa), preferably less than about 25 psi (about 172.37 kPa), morepreferably less than about 15 psi (about 103.42 kPa). It has beendiscovered that the abrasive article used in the method according to thepresent disclosure provides a good cut rate at an exemplified interfacepressure. Also, two or more processing conditions within a planarizationprocess may be used. For example, a first processing segment maycomprise a higher interface pressure than a second processing segment.Rotation and translational speeds of the wafer and/or the abrasivearticle also may be varied during the planarization process.

Working Liquids

Wafer surface processing is preferably conducted in the presence of aworking liquid, which is selected based upon the composition of thewafer surface. In some applications, the working liquid typicallycomprises water, this water can be tap water, distilled water ordeionized water. The working liquid aids processing in combination withthe abrasive article through a chemical mechanical polishing process.Typically the working liquid exhibits a pH from 4 to 12. In certainapplications, a narrower pH may be preferred, for example, greater than7 to about 11. The pH of the working liquid may be advantageouslyadjusted for particular wafer surface materials and CMP processes. Forexample, for removal of surface oxide materials at high removal rates,the pH is generally no less than about 7, more preferably greater thanabout 8, most preferably greater than about 9. The upper limit of pHused in removal of surface oxide materials is generally no greater thanabout 12, preferably less than about 11, and more preferably about 10.5.

One particularly useful working liquid is an aqueous solution thatincludes a variety of different additives. Suitable additives include pHadjusting agents (e.g. acids or bases), as well as complexing,oxidizing, or passivating agents, surfactants, wetting agents, buffers,rust inhibitors, lubricants, soaps, or combinations of these additives.Additives may also include agents which are reactive with the secondmaterial, e.g., metal or metal alloy conductors on the wafer surfacesuch as oxidizing, reducing, passivating, or complexing agents.

For example, during the chemical portion of polishing, the workingliquid may react with the outer or exposed wafer surface. Then duringthe mechanical portion of processing, the abrasive article may removethis reaction product. For example, during the processing of metalsurfaces, it is preferred that the working liquid is an aqueous solutionwhich includes a chemical etchant such as an oxidizing material oragent. For example, chemical polishing of copper may occur when anoxidizing agent in the working liquid reacts with the copper to form asurface layer of copper oxides. The mechanical process occurs when theabrasive article removes this metal oxide from the wafer surface.Alternatively, the metal may first be removed mechanically and thenreact with ingredients in the working fluid.

Other useful chemical additives include complexing agents, which may beetchants or pH buffers, e.g. pH buffers that comprise a basic pHadjusting agents paired with an acidic complexing agent. Thesecomplexing agents may function in a manner similar to the oxidizingagents previously described in that the chemical interaction between thecomplexing agent and the wafer surface creates a layer which is morereadily removed by the mechanical action of the abrasive composites.

When a wafer comprises copper, specific copper etchants may be used asdescribed in Coombs, Printed Circuits Handbook, 4^(th) Ed. Chemicaletchants typically contain oxidizing agents with or without acids.Suitable chemical etchants include sulfuric acid; hydrogen peroxide;cupric chloride; persulfates of ammonium, sodium and potassium; ferricchloride; chromic-sulfuric acids; potassium ferricyanide; nitric acid,and combinations thereof. Examples of suitable complexing agents includealkaline ammonia such as ammonium hydroxide with ammonium chloride andother ammonium salts and additives, ammonium carbonate, ferric nitrate,and combinations thereof. Numerous additives can be added for stability,surface treatment, or etch rate modifiers. Some additives are known toprovide an isotropic etch; i.e., the same etch rate or removal rate inall directions.

Suitable oxidizing, or bleaching agents that may be incorporated into aworking fluid include transition metal complexes such as ferricyanide,ammonium ferric EDTA, ammonium ferric citrate, ferric citrate, ammoniumferric oxalate, cupric citrate, cupric oxalate, cupric gluconate, cupricglycinate, cupric tartrate, and the like where the complexing agent istypically a multidentate amine, carboxylic acid, or combination of thetwo. Numerous coordination compounds are described in Cotton &Wilkinson, Advanced Inorganic Chemistry, 5^(th) Ed. Those with oxidizingpotentials suitable for the oxidation of copper metal and/or cuprousoxide could be used, such as coordination compounds including vanadium,chromium, manganese, cobalt, molybdenum, and tungsten.

Other suitable oxidizing agents include oxo acids of the halogens andtheir salts, such as the alkali metal salts. These acids are describedin Cotton & Wilkinson, Advanced Inorganic Chemistry 5^(th) Ed. Theanions of these acids typically contain halide atoms such as: chlorine,bromine, or iodine. These halides are bonded to one, two, three, or fouroxygen atoms. Examples include: chloric acid (HOClO2); chlorous acid(HOClO); hypochlorous acid (HOCl); and the respective sodium saltsthereof. For example, sodium chlorate, sodium chlorite, and sodiumhypochlorite. Similar bromine and iodine analogs are known.

For processing a wafer that contains copper, the preferred oxidizingagents include nitric acid, hydrogen peroxide, and potassiumferricyanide. Other suitable oxidizing agents are listed in West et al.,Copper and Its Alloys, (1982), and in Leidheiser, The Corrosion ofCopper, Tin, and Their Alloys, (1971). The concentration of theoxidizing agent in deionized water is typically from about 0.01 to 50%by weight, preferably 0.02 to 40% by weight.

The oxidation and dissolution of copper metal can be enhanced by theaddition of complexing agents: ligands and/or chelating agents forcopper. These compounds can bond to copper to increase the solubility ofcopper metal or copper oxides in water as generally described in Cotton& Wilkinson; and Hathaway in Comprehensive Coordination Chemistry, Vol.5; Wilkinson, Gillard, McCleverty, Eds. Suitable additives that may beadded to or used in the working liquid include monodentate complexingagents, such as ammonia, amines, halides, pseudohalides, carboxylates,thiolates, and the like also called ligands. Other additives that may beadded to the working liquid include multidentate complexing agents,typically multidentate amines, and multidentate carboxylic acids.Suitable multidentate amines include ethylenediamine,diethylene-triamine, triethylenetetramine, or combinations thereof.Suitable multidentate carboxylic acids and/or their salts include citricacid, tartaric acid, oxalic acid, gluconic acid, nitriloacetic acid, orcombinations thereof. Combinations of the two monodentate andpolydentate complexing agents include amino acids such as glycine, andcommon analytical chelating agents such asEDTA-ethylenediaminetetraacetic acid and its numerous analogs.

Additional chelators include: polyphosphates, 1,3-diketones,aminoalcohols, aromatic heterocyclic bases, phenols, aminophenols,oximes, Schiff bases, and sulfur compounds.

Similarly for processing a wafer that contains copper, the preferredcomplexing agents are ammonium hydroxide and ammonium carbonate. Theconcentration of the complexing agent in deionized water is typicallyfrom about 0.01 to 50% by weight, preferably 0.02 to 40% by weight.Complexing agents may be combined with oxidizing agents. Other suitablecomplexing agents are listed in West et al., Copper and Its Alloys,(1982), and in Leidheiser, The Corrosion of Copper, Tin, and TheirAlloys, (1971).

Copper and its alloys are used in many environments and applicationsbecause of their excellent corrosion resistance. The nature of thecopper surface in contact with a solution is related to the pH of thesolution as well as the electrochemical potential of the copper. At lowpH, and at high pH, copper tends to corrode. At near neutral pH andslightly basic pH, copper is passivated by copper oxide coating(s):these coatings can be cuprous oxide as well as cupric oxide. To thosewell acquainted to the art of abrasive surface treatment, the nature ofthe surface, i.e., metal or metal oxide, can have a significant effecton the action of the abrasive. Thus, the pH of the polishing solutioncan be important, as well as additives which can act as corrosioninhibitors and/or passivating agents.

Buffers may be added to the working liquid to control the pH and thusmitigate pH changes from minor dilution from rinse water and/ordifference in the pH of the deionized water depending on the source. Asmentioned above, the pH can have a significant effect on the nature ofthe copper surface, and the copper removal rate. The most preferredbuffers are compatible with semiconductor, post-CMP cleaning needs aswell as having reduced potential impurities such as alkali metals. Inaddition, the most preferred buffers can be adjusted to span the pHrange from acidic to near-neutral to basic. Polyprotic acids act asbuffers, and when fully or partially neutralized with ammonium hydroxideto make ammonium salts, they are preferred representative examplesincluding systems of phosphoric acid-ammonium phosphate; polyphosphoricacid-ammonium polyphosphate; the boric acid-ammonium tetraborate; boricacid-ammonium pentaborate.

Other tri- and polyprotic protolytes and their salts, especiallyammonium salts are preferred. These may include ammonium ion buffersystems based on the following protolytes, all of which have at leastone pKa greater than 7: aspartic acid, glutamic acid, and amino acids,including, for example, alanine, proline, glycine, histidine, lysine,arginine, ornithine, cysteine, tyrosine, and dipeptides formed from twoamino acids, for example, carnosine (a dipeptide formed from alanine andhistidine).

Corrosion inhibitors for metals are well known, especially for steel andgalvanized steel. Corrosion inhibitors for copper are often not coveredin the general texts on corrosion inhibitors, but comprise a morespecialized technology. The best known and most widely used inhibitorsfor copper are benzotriazole and its derivatives known as azolederivatives, such as tolyltriazole. Copper is known to be somewhatpassivated by cuprous oxide, especially at neutral or mildly alkalinepH. In addition, phosphates are known in passivating coatings for zincand steel. The addition of the passivating agent may protect areas of ametal surface not yet in contact with the abrasive article frompremature, excessive removal by an etchant or control how much oxidizingagent reacts with the exposed metal surface. An example of a passivatingagent is benzotriazole. Other passivating agents are listed inLeidheiser, The Corrosion of Copper, Tin, and Their Alloys, (1971), pp.119-123. The amount and type of passivating agent will depend in part ofthe desired planarization criteria (cut rate, surface finish andplanarity) The working liquid may also contain additives such assurfactants, wetting agents, buffers, rust inhibitors, lubricants,soaps, and the like. These additives are chosen to provide the desiredbenefit without damaging the underlying semiconductor wafer surface. Alubricant, for example, may be included in the working liquid for thepurpose of reducing friction between the abrasive article and thesemiconductor wafer surface during planarization.

Inorganic particulates may also be included in the working liquid. Theseinorganic particulates may aid in the cut rate. Examples of suchinorganic particulates include: silica, zirconia, calcium carbonate,chromia, ceria, cerium salts (e.g., cerium nitrate), garnet, silicatesand titanium dioxide. The average particle size of these inorganicparticulates should be less than about 1,000 Angstroms, preferably lessthan about 500 Angstroms and more preferably less than about 250Angstroms.

Although particulates may be added to the working liquid, the preferredworking liquid is substantially free of inorganic particulates, e.g.,loose abrasive particles which are not associated with the abrasivearticle. Preferably, the working liquid contains less than 1% by weight,preferably less than 0.1% by weight and more preferably 0% by weightinorganic particulates.

One suitable working liquid comprises a chelating agent, an oxidizingagent, an ionic buffer, and a passivating agent. Such a working liquidmay comprise by weight percent: 3.3% hydrogen peroxide; 93.1% water;3.0% (NH₄)₂HPO₄, 0.5% (NH₄)₃ Citrate and 0.1% 1-H-benzotriazole.Typically, the solution is used for polishing copper wafers. Anothersuitable working liquid comprises an oxidizing agent, an acid, and apassivating agent. Such a working solution may comprise by weightpercent: 15.0% hydrogen peroxide, 0.425% phosphoric acid, 0.2%1-H-benzotriazole, with the remaining percent being water.

In other applications, for example the removal of an oxide material(e.g. silicon dioxide) from the wafer surface, it is presently preferredthat the working liquid is an aqueous solution which includes one ormore of a pH adjusting agent (e.g. an acid or a base), a pH buffer (e.g.a strong acid or base and its conjugate weak base or acid), a complexingagent (e.g. a chemical agent which chelates to, or forms a chemicalcomplex with, another chemical species, for example, a metal ion).

In some applications for the selective removal of a dielectric (e.g. anoxide material such as silicon dioxide) from a surface deployed over abarrier material (e.g. a nitride material such as silicon nitride), itis presently preferred to use an aqueous solution of a pH buffercomprising a basic pH adjusting agent paired with an acidic complexingagent, and a surfactant. The basic pH adjusting agent may be selectedfrom alkali metal hydroxides (e.g. sodium hydroxide, potassiumhydroxide, lithium hydroxide, and the like), alkaline earth metalhydroxides (e.g. calcium hydroxide, magnesium hydroxide, bariumhydroxide, and the like), ammonium hydroxide, and mixtures thereof. Insome exemplary embodiment, the basic pH adjusting agent is generallypresent in an amount sufficient to obtain a pH generally no less thanabout 7, more preferably greater than about 8, most preferably greaterthan about 9; and generally no greater than about 12, preferably lessthan about 11, and more preferably less than about 10.

The acidic complexing agent is preferably a multidentate acidiccomplexing agent, more preferably at least one of an amino acid or adipeptide formed from an amino acid. Suitable amino acids includealanine, proline, glycine, histidine, lysine, arginine, ornithene,cysteine, tyrosine, and combinations thereof. A preferred acidicmultidentate complexing agent is the amino acid praline, more preferablyL-proline. The acidic complexing agent is generally present in an amountfrom about 0.1% w/w (i.e. percent by weight based on the workingliquid), more preferably at least about 1% w/w, even more preferably atleast about 2% w/w, and most preferably about 2.5% w/w; and generally nomore than about 5% w/w, more preferably no more than 4% w/w, and evenmore preferably less than about 3% w/w based on the weight of theworking liquid.

The surfactant is generally a water soluble surfactant, with nonionicsurfactants being preferred. Generally, the nonionic surfactant exhibitsa calculated hydrophile-lipophile balance (i.e. HLB), calculated as theweight percent of hydrophile in the surfactant molecule divided by 5, ofat least about 4, more preferably at least about 6, even more preferablyat least about 8, and most preferably at least about 10. The calculatedHLB is generally no greater than 20. In some embodiments, the surfactantis a fluorochemical surfactant, that is, the surfactant moleculecomprises one or more fluorine atoms.

The nonionic surfactant may be advantageously selected from a linearprimary alcohol ethoxylate, a secondary alcohol ethoxylate, a branchedsecondary alcohol ethoxylate, an octylphenol ethoxylate, an acetylenicprimary alcohol ethoxylate, an acetylenic primary di-alcohol ethoxylate,an alkane di-alcohol, a hydroxyl-terminated ethylene oxide-propyleneoxide random copolymer, a fluoroaliphatic polymeric ester, and mixturesthereof. Generally, the nonionic surfactant may be present in theworking liquid in an amount of at least about 0.025% w/w, morepreferably at least about 0.05% w/w, even more preferably about 0.1%w/w. The upper limit of surfactant concentration in the working liquidis generally at most about 1% w/w, more preferably at most about 0.5%w/w, even more preferably at most about 0.2% based on the weight of theworking liquid. In certain preferred embodiments, the surfactant may bepresent at a concentration of at least the critical micelleconcentration (CMC), and no greater than about five times the criticalmicelle concentration.

In one exemplary presently preferred embodiment, the working liquidcomprises a basic pH adjusting agent such as ammonium hydroxide in anamount sufficient to produce a pH from about 10 to about 11, an acidiccomplexing agent such as L-proline in an amount from about 2% w/w toabout 4% w/w based on the working liquid, and surfactant such as anethoxylated alcohol (e.g. Tergitol™ 15-S-7, available from Dow ChemicalCo., Midland, Mich.) in an amount from about 0.05% w/w to about 1% w/wbased on the weight working liquid.

In certain exemplary embodiments, the surfactant is selected to be afluorochemical surfactant. In other exemplary embodiments, thesurfactant is selected to be a nonionic surfactant, and the workingliquid additionally includes water, a polyelectrolyte, and a buffercomprising a basic pH adjusting agent and an acidic complexing agent. Insuch embodiments, the preferred pH may be generally from about 7 toabout 12.

The amount of the working liquid is preferably sufficient to aid in theremoval of metal or metal oxide deposits from the surface. In manyinstances, there is sufficient liquid from the basic working liquidand/or the chemical etchant. However, in some instances it is preferredto have a second liquid present at the planarization interface inaddition to the first working liquid. This second liquid may be the sameas the liquid from the first liquid, or it may be different.

Fixed Abrasive Article

The fixed abrasive article is preferably long lasting, e.g., the fixedabrasive article should be able to complete at least two, preferably atleast 5, more preferably at least 20, and most preferably at least 30,different wafers. The abrasive article may contain a backing. Abrasiveparticles are dispersed in a binder to form textured andthree-dimensional abrasive composites which are fixed, adhered, orbonded to a backing. Optionally, the fixed abrasive article does nothave to have a separate backing.

In some exemplary embodiments, the fixed abrasive article comprises asurfactant coated on the surface a surface of the fixed abrasivearticle. In certain exemplary embodiments, the fixed abrasive articleincludes a plurality of three-dimensional abrasive composites fixed toan abrasive article, the three-dimensional abrasive compositescomprising a plurality of abrasive particles fixed and dispersed in abinder; and a surfactant disposed on at least a portion of a surface ofthe three-dimensional abrasive composites.

In certain additional exemplary embodiments, a method of preparing afixed abrasive article including a surfactant for use in modifying asurface of a wafer in a chemical mechanical polishing process includes:

a. providing a fixed abrasive article having a surface comprising aplurality of three-dimensional abrasive composites fixed to an abrasivearticle, the three-dimensional abrasive composites comprising aplurality of abrasive particles fixed and dispersed in a binder;

b. exposing the surface to a surfactant solution in a solvent;

c. drying the fixed abrasive article to remove at least a portion of thesolvent, thereby forming a coating of surfactant on at least a portionof the surface.

In certain optional embodiments, steps (a)-(c) are repeated at apolishing rate until a target polishing rate is obtained, and thepolishing rate thereafter remains within about 200 Å/min of the targetpolishing rate, when the fixed abrasive article is used to polish aplurality of wafer surfaces. In particular exemplary embodiments, thesolvent may be an aqueous solvent (e.g. water), a nonaqueous solvent(e.g. an alcohol or other organic solvent), or a mixture of an aqueousand a nonaqueous solvent (e.g. ethanol and water).

The abrasive article should preferably provide a good cut rate.Additionally, the abrasive article is preferably capable of yielding asemiconductor wafer having an acceptable flatness, surface finish andminimal dishing. The materials, desired texture, and process used tomake the abrasive article all influence whether or not these criteriaare met.

In the abrasive articles used in the inventive methods described herein,the abrasive composites are “three-dimensional” such that there arenumerous abrasive particles throughout at least a portion of thethickness of the abrasive article.

The abrasive article also has a “texture” associated with it, i.e., itis a “textured” abrasive article. This can be seen with reference to theabrasive articles illustrated in FIG. 4 and described above, in whichthe pyramid-shaped composites are the raised portions and in which thevalleys between the pyramids are the recessed portions.

The recessed portions may act as channels to help distribute the workingliquid over the entire wafer surface. The recessed portions may also actas channels to help remove the worn abrasive particles and other debrisfrom the wafer and abrasive article interface. The recessed portions mayalso prevent the phenomenon known in the art as “stiction”. If theabrasive composite is smooth rather than textured, an abrasive articletends to stick to or become lodged against the wafer surface. Finally,the recessed portions allow a higher unit pressure on the raisedportions of the abrasive article and, thus help to expunge expelledabrasive particles from the abrasive surface and expose new abrasiveparticles.

The abrasive article of the disclosure may be circular in shape, e.g.,in the form of an abrasive disc. The outer edges of the circularabrasive disc are preferably smooth or, alternatively, may be scalloped.The abrasive article may also be in the form of an oval or of anypolygonal shape such as triangular, square, rectangular, and the like.Alternatively, the abrasive article may be in the form of a belt inanother embodiment. The abrasive article may be provided in the form ofa roll, typically referred to in the abrasive art as abrasive taperolls. In general, the abrasive tape rolls will be indexed during themodification process. The abrasive article may be perforated to provideopenings through the abrasive coating and/or the backing to permit thepassage of the liquid medium before, during or after use.

Backing

The abrasive article may include a backing. It is preferred that thebacking be very uniform in thickness. If the backing is not sufficientlyuniform in thickness, a greater variability in the wafer uniformity mayresult. A variety of backing materials are suitable for this purpose,including both flexible backings and backings that are more rigid.Examples of flexible abrasive backings include polymeric film, primedpolymeric film, metal foil, cloth, paper, vulcanized fiber, nonwovensand treated versions thereof and combinations thereof. One preferredtype of backing is a polymeric film. Examples of such films includepolyester films, polyester and co-polyester films, microvoided polyesterfilms, polyimide films, polyamide films, polyvinyl alcohol films,polypropylene film, polyethylene film, and the like. The thickness ofthe polymeric film backing generally ranges between about 20 to 1,000micrometers, preferably between 50 to 500 micrometers and morepreferably between 60 to 200 micrometers.

There should also be good adhesion between the polymeric film backingand the binder. In many instances, abrasive composite coated surface ofpolymeric film backing is primed to improve adhesion. The primer mayinvolve surface alteration or application of a chemical-type primer.Examples of surface alterations include corona treatment, UV treatment,electron beam treatment, flame treatment and scuffing to increase thesurface area. Examples of chemical-type primers include polyvinylidenechlorides and ethylene acrylic acid copolymers reported in U.S. Pat. No.3,188,265; colloidal dispersions reported in U.S. Pat. No. 4,906,523;and aziridine-type materials reported in U.S. Pat. No. 4,749,617.

Suitable alternative backings include an embossed polymeric film (e.g.,a polyester, polyurethane, polycarbonate, polyamide, polypropylene, orpolyethylene film) or embossed cellulosic backing (e.g., paper or othernonwoven cellulosic material). The embossed backing may also belaminated to a non-embossed material to form the backing. The embossedpattern can be any texture. For example, the pattern can be in the formof frustums of spheres, pyramids, truncated pyramids, cones, cubes,blocks, rods, and the like. The pattern may also be hexagonal arrays,ridges, or lattices. It is also possible to have ridges made ofgeometric shapes such as prisms.

Another alternative backing may also be a foamed backing, e.g., apolymeric foam such as a polyurethane foam. It is within the scope ofthis disclosure to apply the abrasive composite directly to the frontsurface of the subpad. Thus, the abrasive composite is directly bondedto the subpad.

A pressure sensitive adhesive can be laminated to the nonabrasive sideof the backing. The pressure sensitive adhesive can be coated directlyonto the back surface of the backing. Alternatively, the pressuresensitive adhesive can be a transfer tape that is laminated to the backsurface of the backing. In another aspect of the disclosure, a foamsubstrate can be laminated to the backing.

Abrasive Particles

The abrasive composites comprise abrasive particles and a binder. Thebinder fixes abrasive particles to an abrasive article so that duringthe wafer modification process, the abrasive particles do not readilydisassociate from the abrasive article. The abrasive particles may behomogeneously dispersed in the binder or alternatively the abrasiveparticles may be non-homogeneously dispersed. The term “dispersed”refers to the abrasive particles being distributed throughout thebinder. It is generally preferred that the abrasive particles behomogeneously dispersed so that the resulting abrasive coating providesa more consistent modification process.

For modifying or refining wafer surfaces, fine abrasive particles arepreferred. The average particle size of the abrasive particles may rangefrom about 0.001 to 50 micrometers, typically between 0.01 to 10micrometers. It is preferred that the average particle is less thanabout 5 micrometers, more preferably less than about 3 micrometers. Insome instances the average particle is about 0.5 micrometers or evenabout 0.3 micrometers. The particle size of the abrasive particle istypically measured by the longest dimension of the abrasive particle. Inalmost all cases there will be a range or distribution of particlesizes. In some instances it is preferred that the particle sizedistribution be tightly controlled such that the resulting abrasivearticle provides a very consistent surface finish on the wafer. Theabrasive particles may also be present in the form of an abrasiveagglomerate. The abrasive particles in the agglomerate may be heldtogether by an agglomerate binder. Alternatively, the abrasive particlesmay bond together by inter particle attraction forces.

Examples of suitable abrasive particles include fused aluminum oxide,heat treated aluminum oxide, white fused aluminum oxide, porousaluminas, transition aluminas, zirconia, tin oxide, ceria, fused aluminazirconia, or alumina-based sol gel derived abrasive particles. Thealumina abrasive particle may contain a metal oxide modifier. Examplesof alumina-based sol gel derived abrasive particles can be found in U.S.Pat. Nos. 4,314,827; 4,623,364; 4,744,802; 4,770,671; and 4,881,951.

For wafer surfaces that contain aluminum, the preferred abrasiveparticles are alpha alumina, chi alumina, and other transition aluminas.For semiconductor wafers that contain copper, the preferred abrasiveparticles are alpha alumina. The alpha alumina abrasive particles can befused aluminum oxide abrasive particles. A preferred form of fine alphaalumina particles is fine alpha alumina particles having internalporosity. Porous alumina particles are typically formed by heating aporous transition alumina particle for a brief period of time at atemperature at which it will convert to the alpha form. This alphaalumina transformation always involves a significant decrease in surfacearea, but if the alpha alumina particles are exposed to the conversiontemperature for a brief period of time, the resulting particles willcontain internal porosity. The pores or voids in these particles aremuch coarser than those in the transition alumina particles. Whereas inthe case of transition aluminas the pore diameters are in the range ofabout 1 to about 30 nm, the pores in the porous alpha alumina particlesare in the range of about 40 to about 200 nm. The time required for thisconversion to alpha alumina will depend on the purity of the alumina,and the particle size and crystallinity of the transition alumina. Ingeneral, the transition alumina is heated in the temperature range of1,000 to 1400° C. for tens of seconds to minutes. An explanation of thistransformation process is reported by Wefers et al., Oxides andHydroxides of Aluminum (1987), published by Alcoa Company of America. Acommercial source of alpha alumina abrasive particles less than onemicrometer is commercially available from Praxair Surface Technologiesof Indianapolis, Ind. The chi alumina particles can be a porous chialumina particle that is formed by calcining an alumina hydrate such asalumina trihydrate. A commercial source of alumina trihydrate abrasiveparticles is Huber Engineered Minerals, Norcross, Ga. Ceria abrasiveparticles may be purchased from Rhone Poulenc; Shelton, Conn.;Transelco, N.Y.; Fujimi, Japan; Molycorp, Fairfield, N.J.; American RarOx, Chaveton City, Mass.; and Nanophase, Burr Ridge, Ill. Sources foralumina are Alcan Chemicals, Alcan Aluminum Corporation, Cleveland, Ohioand Condea Chemie GMBH, Hamburg, Germany. The ceria abrasive particlesmay either be essentially free of modifiers or dopants (e.g., othermetal oxides) or may contain modifiers and/or dopants (e.g., other metaloxides). In some instances, these metal oxides may react with ceria. Itis also feasible to use ceria with a combination of two or more metaloxide modifiers. These metal oxides may react with the ceria to formreaction products.

The abrasive article may also contain a mixture of two or more differenttypes of abrasive particles. The abrasive particles may be of differenthardnesses. In the mixture of two or more different abrasive particles,the individual abrasive particles may have the same average particlesize, or may have a different average particle size.

In some instances it is preferred to modify or treat the surface of theabrasive particles with an additive. These additives may improve thedispersibility of the abrasive particles in the binder precursor and/orimprove the adhesion to the binder precursor and/or the binder. Abrasiveparticle treatment may also alter and improve the cuttingcharacteristics of the treated abrasive particles. Further treatment mayalso substantially lower the viscosity of the binder precursor/abrasivearticle slurry. The lower viscosity also permits higher percentages ofabrasive particles to be incorporated into an abrasive slurry formed ofa binder precursor and abrasive particles. Another potential advantageof a surface treatment is to minimize the agglomeration of the abrasiveparticles. Examples of suitable surface modification additives includewetting agents (sometimes referred to as surfactants) and couplingagents. A coupling agent may provide an association bridge between thebinder and the abrasive particles. Examples of suitable coupling agentsinclude silanes, titanates, and zircoaluminates. Examples ofcommercially available coupling agents include “A174” and “A1230” fromOSI Specialties, Inc., Danbury, Conn. Still another example of such acoupling agent for ceria abrasive particles is isopropyl triisosteroyltitanate. Examples of commercial wetting agents are Disperbyk 111available from Byk Chemie, Wallingford, Conn. and FP4 available from ICIAmerica Inc., Wilmington, Del. There are various means to incorporatethese surface treatments into the abrasive article. For example, thesurface treatment agent may be added directly to the abrasive slurryduring the manufacture of the abrasive article. In yet another mode, thesurface treatment agent may be applied to the surface of the abrasiveparticles prior to being incorporated into the abrasive slurry.

Filler Particles

The abrasive composite may optionally contain filler particles. Thefiller may alter the erodibility of the abrasive composite. In someinstances with the appropriate filler and amount, the filler maydecrease the erodibility of the abrasive composite. Conversely, in someinstances with the appropriate filler and amount, the filler mayincrease the erodibility of the abrasive composite. Fillers may also beselected to reduce cost of the abrasive composite, alter the rheology ofthe slurry, and/or to alter the abrading characteristics of the abrasivecomposite. Fillers are typically selected so as not to deleteriouslyaffect the desired modification criteria. Examples of useful fillers forcertain embodiments of this disclosure include alumina trihydrates,magnesium silicate, thermoplastic particles and thermoset particles.Other miscellaneous fillers include inorganic salts, sulfur, organicsulfur compounds, graphite, boron nitride, and metallic sulfides. Theseexamples of fillers are meant to be a representative showing of someuseful fillers, and are not meant to encompass all useful fillers. Insome instances, it is preferable to use a blend of two or more differentparticle sizes of filler. The filler may be equant or acicular. Fillersmay be provided with a surface treatment as described above for abrasiveparticles. The fillers should not cause excessive scratching of theexposed surfaces.

Binders

The exposed wafer surface of a semiconductor is modified with anabrasive article that contains a plurality of abrasive particlesdispersed in a binder. The particular chemistry of the binder isimportant to the performance of the abrasive article. For example, ifthe binder is “too hard”, the resulting abrasive article may create deepand unacceptable scratches in the exposed metal surface. Conversely, ifthe binder is “too soft”, the resulting abrasive article may not providea sufficient metal cut rate during the modification process or may havepoor article durability. Thus, the binder is selected to provide thedesired characteristics of the abrasive article.

The preferred binders are free radical curable binder precursors. Thesebinders are capable of polymerizing rapidly upon exposures to thermalenergy or radiation energy. One preferred subset of free radical curablebinder precursors include ethylenically unsaturated binder precursors.Examples of such ethylenically unsaturated binder precursors includeaminoplast monomers or oligomers having pendant alpha, beta unsaturatedcarbonyl groups, ethylenically unsaturated monomers or oligomers,acrylated isocyanurate monomers, acrylated urethane oligomers, acrylatedepoxy monomers or oligomers, ethylenically unsaturated monomers ordiluents, acrylate dispersions, and mixtures thereof. The term acrylateincludes both acrylates and methacrylates.

The binders for the abrasive articles of this disclosure are preferablyformed from an organic binder precursor. The binder precursor preferablyis capable of flowing sufficiently so as to be coatable, and thensolidifying. Solidification may be achieved by curing (e.g.,polymerizing and/or crosslinking) and/or by drying (e.g., driving off aliquid), or simply upon cooling. The binder precursor may be an organicsolvent-borne, a water-borne, or a 100% solids (i.e., a substantiallysolvent-free) composition. Both thermoplastic and thermosetting polymersor materials, as well as combinations thereof, may be used as the binderprecursor.

In many instances, the abrasive composite is formed from a slurry of amixture of abrasive particles and a binder precursor. The abrasivecomposite may comprise by weight between about 1 part abrasive particlesto 95 parts abrasive particles and 5 parts binder to 99 parts binder.Preferably the abrasive composite comprises about 30 to 85 partsabrasive particles and about 15 to 70 parts binder. Likewise theabrasive composite may comprise based upon volume of abrasive compositehaving 0.2 to 0.8 parts abrasive particles and 0.2 to 0.8 parts binderprecursor. This volume ratio is based just upon the abrasive particlesand binder precursor, and does not include the volume contribution ofthe backing or optional fillers or additives.

The binder precursor is preferably a curable organic material (i.e., apolymer or material capable of polymerizing and/or crosslinking uponexposure to heat and/or other sources of energy, such as e-beam,ultraviolet, visible, etc., or with time upon the addition of a chemicalcatalyst, moisture, or other agent which cause the polymer to cure orpolymerize). Binder precursor examples include epoxy polymers, aminopolymers or aminoplast polymers such as alkylated urea-formaldehydepolymers, melamine-formaldehyde polymers, and alkylatedbenzoguanamine-formaldehyde polymer, acrylate polymers includingacrylates and methacrylates such as vinyl acrylates, acrylated epoxies,acrylated urethanes, acrylated polyesters, acrylated polyethers, vinylethers, acrylated oils, and acrylated silicones, alkyd polymers such asurethane alkyd polymers, polyester polymers, reactive urethane polymers,phenolic polymers such as resole and novolac polymers, phenolic/latexpolymers, epoxy polymers such as bisphenol epoxy polymers, isocyanates,isocyanurates, polysiloxane polymers including alkylalkoxysilanepolymers, or reactive vinyl polymers. The polymers may be in the form ofmonomers, oligomers, polymers, or combinations thereof.

The preferred aminoplast binder precursors have at least one pendantalpha, beta-unsaturated carbonyl group per molecule or oligomer. Thesepolymer materials are further described in U.S. Pat. Nos. 4,903,440(Larson et al.) and 5,236,472 (Kirk et al.).

Ethylenically unsaturated binder precursors include both monomeric andpolymeric compounds that contain atoms of carbon, hydrogen and oxygen,and optionally, nitrogen and the halogens. Oxygen or nitrogen atoms orboth are generally present in ether, ester, urethane, amide, and ureagroups. The ethylenically unsaturated monomers may be monofunctional,difunctional, trifunctional, tetrafunctional or even higherfunctionality, and include both acrylate and methacrylate-basedmonomers. Suitable ethylenically unsaturated compounds are preferablyesters made from the reaction of compounds containing aliphaticmonohydroxy groups or aliphatic polyhydroxy groups and unsaturatedcarboxylic acids, such as acrylic acid, methacrylic acid, itaconic acid,crotonic acid, isocrotonic acid, or maleic acid. Representative examplesof ethylenically unsaturated monomers include methyl methacrylate, ethylmethacrylate, styrene, divinylbenzene, hydroxy ethyl acrylate, hydroxyethyl methacrylate, hydroxy propyl acrylate, hydroxy propylmethacrylate, hydroxy butyl acrylate, hydroxy butyl methacrylate, laurylacrylate, octyl acrylate, caprolactone acrylate, caprolactonemethacrylate, tetrahydrofurfuryl methacrylate, cyclohexyl acrylate,stearyl acrylate, 2-phenoxyethyl acrylate, isooctyl acrylate, isobornylacrylate, isodecyl acrylate, polyethylene glycol monoacrylate,polypropylene glycol monoacrylate, vinyl toluene, ethylene glycoldiacrylate, polyethylene glycol diacrylate, ethylene glycoldimethacrylate, hexanediol diacrylate, triethylene glycol diacrylate, 2(2-ethoxyethoxy)ethyl acrylate, propoxylated trimethylol propanetriacrylate, trimethylolpropane triacrylate, glycerol triacrylate,pentaerthyitol triacrylate, pentaerythritol trimethacrylate,pentaerythritol tetraacrylate and pentaerythritol tetramethacrylate.Other ethylenically unsaturated materials include monoallyl, polyallyl,or polymethallyl esters and amides of carboxylic acids, such as diallylphthalate, diallyl adipate, or N,N-diallyladipamide. Still othernitrogen containing ethylenically unsaturated monomers includetris(2-acryl-oxyethyl)isocyanurate,1,3,5-tri(2-methyacryloxyethyl)-s-triazine, acrylamide,methylacrylamide, N-methyl-acrylamide, N,N-dimethylacrylamide,N-vinyl-pyrrolidone, or N-vinyl-piperidone.

A preferred binder precursor contains a blend of two or more acrylatemonomers. For example, the binder precursor may be a blend oftrifunctional acrylate and a monofunctional acrylate monomers. Anexample of one binder precursor is a blend of propoxylated trimethylolpropane triacrylate and 2 (2-ethoxyethoxy)ethyl acrylate. The weightratios of multifunctional acrylate and monofunctional acrylate polymersmay range from about 1 part to about 90 parts multifunctional acrylateto about 10 parts to about 99 parts monofunctional acrylate.

It is also feasible to formulate a binder precursor from a mixture of anacrylate and an epoxy polymer, e.g., as described in U.S. Pat. No.4,751,138 (Tumey et al.).

Other binder precursors include isocyanurate derivatives having at leastone pendant acrylate group and isocyanate derivatives having at leastone pendant acrylate group are further described in U.S. Pat. No.4,652,274 (Boettcher et al.). The preferred isocyanurate material is atriacrylate of tris(hydroxy ethyl)isocyanurate.

Still other binder precursors include diacrylate urethane esters as wellas polyacrylate or poly methacrylate urethane esters of hydroxyterminated isocyanate extended polyesters or polyethers. Examples ofcommercially available acrylated urethanes include those under thetradename “UVITHANE 782”, available from Morton Chemical; “CMD 6600”,“CMD 8400”, and “CMD 8805”, available from UCB Radcure Specialties,Smyrna, Ga.; “PHOTOMER” resins (e.g., PHOTOMER 6010) from Henkel Corp.,Hoboken, N.J.; “EBECRYL 220” (hexafunctional aromatic urethaneacrylate), “EBECRYL 284” (aliphatic urethane diacrylate of 1200 dilutedwith 1,6-hexanediol diacrylate), “EBECRYL 4827” (aromatic urethanediacrylate), “EBECRYL 4830” (aliphatic urethane diacrylate diluted withtetraethylene glycol diacrylate), “EBECRYL 6602” (trifunctional aromaticurethane acrylate diluted with trimethylolpropane ethoxy triacrylate),“EBECRYL 840” (aliphatic urethane diacrylate), and “EBECRYL 8402”(aliphatic urethane diacrylate) from UCB Radcure Specialties; and“SARTOMER” resins (e.g., SARTOMER 9635, 9645, 9655, 963-B80, 966-A80,CN980M50, etc.) from Sartomer Co., Exton, Pa.

Yet other binder precursors include diacrylate epoxy esters as well aspolyacrylate or poly methacrylate epoxy ester such as the diacrylateesters of bisphenol A epoxy polymer. Examples of commercially availableacrylated epoxies include those under the tradename “CMD 3500”, “CMD3600”, and “CMD 3700”, available from UCB Radcure Specialties.

Other binder precursors may also be acrylated polyester polymers.Acrylated polyesters are the reaction products of acrylic acid with adibasic acid/aliphatic diol-based polyester. Examples of commerciallyavailable acrylated polyesters include those known by the tradedesignations “PHOTOMER 5007” (hexafunctional acrylate), and “PHOTOMER5018” (tetrafunctional tetracrylate) from Henkel Corp.; and “EBECRYL 80”(tetrafunctional modified polyester acrylate), “EBECRYL 450” (fatty acidmodified polyester hexaacrylate) and “EBECRYL 830” (hexafunctionalpolyester acrylate) from UCB Radcure Specialties.

Another preferred binder precursor is a blend of ethylenicallyunsaturated oligomer and monomers. For example the binder precursor maycomprise a blend of an acrylate functional urethane oligomer and one ormore monofunctional acrylate monomers. This acrylate monomer may be apentafunctional acrylate, tetrafunctional acrylate, trifunctionalacrylate, difunctional acrylate, monofunctional acrylate polymer, orcombinations thereof.

The binder precursor may also be an acrylate dispersion like thatdescribed in U.S. Pat. No. 5,378,252 (Follensbee).

In addition to thermosetting binders, thermoplastic binders may also beused. Examples of suitable thermoplastic binders include polyamides,polyethylene, polypropylene, polyesters, polyurethanes, polyetherimide,polysulfone, polystyrene, acrylonitrile-butadiene-styrene blockcopolymer, styrene-butadiene-styrene block copolymers,styrene-isoprene-styrene block copolymers, acetal polymers, polyvinylchloride and combinations thereof.

Water-soluble binder precursors optionally blended with a thermosettingresin may be used. Examples of water-soluble binder precursors includepolyvinyl alcohol, hide glue, or water-soluble cellulose ethers such ashydroxypropylmethyl cellulose, methyl cellulose or hydroxyethylmethylcellulose. These binders are reported in U.S. Pat. No. 4,255,164 (Butkzeet al.).

The abrasive composites may optionally include a plasticizer. Ingeneral, the addition of the plasticizer will increase the erodibilityof the abrasive composite and soften the overall binder composition. Insome instances, the plasticizer will act as a diluent for the binderprecursor. The plasticizer is preferably compatible with the binder tominimize phase separation. Examples of suitable plasticizers includepolyethylene glycol, polyvinyl chloride, dibutyl phthalate, alkyl benzylphthalate, polyvinyl acetate, polyvinyl alcohol, cellulose esters,silicone oils, adipate and sebacate esters, polyols, polyolsderivatives, t-butylphenyl diphenyl phosphate, tricresyl phosphate,castor oil, or combinations thereof. Phthalate derivatives are one typeof preferred plasticizers.

In the case of binder precursors containing ethylenically unsaturatedmonomers and oligomers, polymerization initiators may be used. Examplesinclude organic peroxides, azo compounds, quinones, nitroso compounds,acyl halides, hydrazones, mercapto compounds, pyrylium compounds,imidazoles, chlorotriazines, benzoin, benzoin alkyl ethers, diketones,phenones, or mixtures thereof. Examples of suitable commerciallyavailable, ultraviolet-activated photoinitiators have tradenames such as“IRGACURE 651” and “IRGACURE 184”, commercially available from the CibaGeigy Company and “DAROCUR 1173”, commercially available from Merck.Another visible light-activated photoinitiator has the trade name“IRGACURE 369”, commercially available from Ciba Geigy Company. Examplesof suitable visible light-activated initiators are reported in U.S. Pat.No. 4,735,632.

A suitable initiator system may include a photosensitizer.Representative photosensitizer may have carbonyl groups or tertiaryamino groups or mixtures thereof. Preferred photosensitizers havingcarbonyl groups are benzophenone, acetophenone, benzil, benzaldehyde,o-chlorobenzaldehyde, xanthone, thioxanthone, 9,10-anthraquinone, orother aromatic ketones. Preferred photosensitizers having tertiaryamines are methyldiethanolamine, ethyldiethanolamine, triethanolamine,phenylmethyl-ethanolamine, or dimethylaminoethylbenzoate. Commerciallyavailable photosensitizers include “QUANTICURE ITX”, “QUANTICURE QTX”,“QUANTICURE PTX”, “QUANTICURE EPD” from Biddle Sawyer Corp.

In general, the amount of photosensitizer or photoinitiator system mayvary from about 0.01 to 10% by weight, more preferably from 0.25 to 4.0%by weight of the components of the binder precursor.

Additionally, it is preferred to disperse (preferably uniformly) theinitiator in the binder precursor before addition of any particulatematerial, such as the abrasive particles and/or filler particles.

In general, it is preferred that the binder precursor be exposed toradiation energy, preferably ultraviolet light or visible light, to cureor polymerize the binder precursor. In some instances, certain abrasiveparticles and/or certain additives will absorb ultraviolet and visiblelight, which may hinder proper cure of the binder precursor. Thisoccurs, for example, with ceria abrasive particles. The use of phosphatecontaining photoinitiators, in particular acylphosphine oxide containingphotoinitiators, may minimize this problem. An example of such anacylphosphate oxide is 2,4,6-trimethylbenzoyldiphenylphosphine oxide,which is commercially available from BASF Corporation under the tradedesignation “LR8893”. Other examples of commercially availableacylphosphine oxides include “DAROCUR 4263” and “DAROCUR 4265”,commercially available from Merck.

Cationic initiators may be used to initiate polymerization when thebinder is based upon an epoxy or vinyl ether. Examples of cationicinitiators include salts of onium cations, such as arylsulfonium salts,as well as organometallic salts such as ion arene systems. Otherexamples are reported in U.S. Pat. Nos. 4,751,138 (Tumey et al.);5,256,170 (Harmer et al.); 4,985,340 (Palazotto); and 4,950,696.

Dual-cure and hybrid-cure photoinitiator systems may also be used. Indual-cure photoinitiator systems, curing or polymerization occurs in twoseparate stages, via either the same or different reaction mechanisms.In hybrid-cure photoinitiator systems, two curing mechanisms occur atthe same time upon exposure to ultraviolet/visible or e-beam radiation.

The abrasive composite may include other additives such as abrasiveparticle surface modification additives, passivating agents, watersoluble additives, water sensitive agents, coupling agents, fillers,expanding agents, fibers, antistatic agents, reactive diluents,initiators, suspending agents, lubricants, wetting agents, surfactants,pigments, dyes, UV stabilizers, complexing agents, chain transferagents, accelerators, catalysts, or activators. The amounts of theseadditives are selected to provide the properties desired.

Water and/or organic solvent may be incorporated into the abrasivecomposite. The amount of water and/or organic solvent is selected toachieve the desired coating viscosity of binder precursor and abrasiveparticles. In general, the water and/or organic solvent should becompatible with the binder precursor. The water and/or solvent may beremoved following polymerization of the precursor, or it may remain withthe abrasive composite.

Examples of ethylenically unsaturated diluents or monomers can be foundin U.S. Pat. No. 5,236,472 (Kirk et al.). In some instances theseethylenically unsaturated diluents are useful because they tend to becompatible with water. Additional reactive diluents are disclosed inU.S. Pat. No. 5,178,646 (Barber et al).

Abrasive Composite Configuration

There are many different forms of three-dimensional, textured, abrasivearticles. Examples of representative forms are schematically illustratedin FIGS. 4, 5, 6, and 7.

Preferred abrasive composites may be precisely shaped (as defined in theSummary above) or irregularly shaped, with precisely shaped compositesbeing preferred.

The individual abrasive composite shape may have the form of any of avariety of geometric solids. Typically the base of the shape in contactwith the backing has a larger surface area than the distal end of thecomposite. The shape of the composite may be selected from among anumber of geometric solids such as a cubic, cylindrical, prismatic,rectangular, pyramidal, truncated pyramidal, conical, hemispherical,truncated conical, cross, or post-like cross sections with a distal end.Composite pyramids may have four sides, five sides or six sides. Theabrasive composites may also have a mixture of different shapes. Theabrasive composites may be arranged in rows, in spirals, in helices, orin lattice fashion, or may be randomly placed.

The sides forming the abrasive composites may be perpendicular relativeto the backing, tilted relative to the backing or tapered withdiminishing width toward the distal end. If the sides are tapered, it iseasier to remove the abrasive composite from the cavities of a mold orproduction tool. The tapered angle may range from about 1 to 75 degrees,preferably from about 2 to 50 degrees, more preferably from about 3 to35 degrees and most preferably between about 5 to 15 degrees. Thesmaller angles are preferred because this results in a consistentnominal contact area as the composite wears. Thus, in general, the taperangle is a compromise between an angle large enough to facilitateremoval of the abrasive composite from a mold or production tool andsmall enough to create a uniform cross sectional area. An abrasivecomposite with a cross section that is larger at the distal end than atthe back may also be used, although fabrication may require a methodother than simple molding.

The height of each abrasive composite is preferably the same, but it ispossible to have composites of varying heights in a single abrasivearticle. The height of the composites with respect to the backing or tothe land between the composites generally may be less than about 2,000micrometers, and more particularly in the range of about 25 to 200micrometers.

The base of the abrasive composites may abut one another oralternatively, the bases of adjacent abrasive composites may beseparated from one another by some specified distance. In someembodiments, the physical contact between adjacent abrasive compositesinvolves no more than 33% of the vertical height dimension of eachcontacting composite. More preferably, the amount of physical contactbetween the abutting composites is in the range of 1 to 25% of thevertical height of each contacting composite. This definition ofabutting also covers an arrangement where adjacent composites share acommon abrasive composite land or bridge-like structure which contactsand extends between facing sidewalls of the composites. Preferably, theland structure has a height of no greater than 33% of the verticalheight dimension of each adjacent composite. The abrasive composite landis formed from the same slurry used to form the abrasive composites. Thecomposites are “adjacent” in the sense that no intervening composite islocated on a direct imaginary line drawn between the centers of thecomposites. It is preferred that at least portions of the abrasivecomposites be separated from one another so as to provide the recessedareas between the raised portions of the composites.

The linear spacing of the abrasive composites may range from about 1abrasive composite per linear cm to about 100 abrasive composites perlinear cm. The linear spacing may be varied such that the concentrationof composites is greater in one location than in another. For example,the concentration may be greatest in the center of the abrasive article.The areal density of composites ranges from about 1 to 10,000composites/cm².

It is also feasible to have areas of the backing exposed, i.e., wherethe abrasive coating does not cover the entire surface area of thebacking. This type of arrangement is further described in U.S. Pat. No.5,014,468 (Ravipati et al.).

The abrasive composites are preferably set out on a backing in apredetermined pattern or set out on a backing at a predeterminedlocation. For example, in the abrasive article made by providing aslurry between the backing and a production tool having cavitiestherein, the predetermined pattern of the composites will correspond tothe pattern of the cavities on the production tool. The pattern is thusreproducible from article to article.

In one embodiment of the predetermined pattern, the abrasive compositesare in an array or arrangement, by which is meant that the compositesare in a regular array such as aligned rows and columns, or alternatingoffset rows and columns. If desired, one row of abrasive composites maybe directly aligned in front of a second row of abrasive composites.Preferably, one row of abrasive composites may be offset from a secondrow of abrasive composites.

In another embodiment, the abrasive composites may be set out in a“random” array or pattern. By this it is meant that the composites arenot in a regular array of rows and columns as described above. Forexample, the abrasive composites may be set out in a manner as describedin WO PCT 95/07797 published Mar. 23, 1995 (Hoopman et al.) and WO PCT95/22436 published Aug. 24, 1995 (Hoopman et al.). It is understood,however, that this “random” array is a predetermined pattern in that thelocation of the composites on the abrasive article is predetermined andcorresponds to the location of the cavities in the production tool usedto make the abrasive article.

The three-dimensional, textured, abrasive article also may have avariable abrasive coating composition. For example, the center of anabrasive disc may contain an abrasive coating that is different (e.g.,softer, harder, or more or less erodible) from the outer region of theabrasive disc.

The abrasive article 40 in FIG. 4 has pyramidal abrasive composites 41fixed or bonded to backing 42. There are recesses or valleys 43 betweenadjacent abrasive composites. There is also a second row of pyramidalabrasive composites offset from the first row. Outermost point or distalend of the pyramidal abrasive composites contacts the wafer surfaceduring processing.

The abrasive article 50 in FIG. 5 has irregular shape, pyramidalabrasive composites. In this particular illustration, the abrasivecomposite has a pyramidal type shape. Boundaries which define thepyramid are irregularly shaped. The imperfect shape can be the result ofthe slurry flowing and distorting the initial shape prior to significantcuring or solidification of the binder precursor. An irregular shape ischaracterized by non-straight, non-clear, non-reproducible, inexact orimperfect planes or shape boundaries.

The abrasive article 60 in FIG. 6 has truncated pyramid abrasivecomposites 61.

The abrasive article 70 in FIG. 7 has both “cross” shape 71 and an “x”shape 72 abrasive composites. The abrasive composites are set out in apattern of rows. The abrasive composites in various rows are offset fromone another and do not directly align with the abrasive composites in anadjacent row. Further, the rows of abrasive composites are separated byspace or valley. The valley or space may contain only a very smallamount (as measured by height) of abrasive composite or may contain noabrasive composite. Another arrangement or configuration of abrasivecomposites is similar to FIG. 6, except that each alternating rowcomprises either abrasive composites having the “cross” shape orabrasive composites having the “x” shape. In this arrangement, theabrasive composites from the odd rows are still offset from the abrasivecomposites from the even rows. In the above described arrangements ofcross-shaped or “x”-shaped composites, it is preferred that the lengthof one line forming either the cross or the x shape is about 750micrometers and the width of one line forming either the cross or the xshape is about 50 micrometers.

A preferred method for making an abrasive article having preciselyshaped abrasive composites is described in U.S. Pat. Nos. 5,152,917(Pieper et al) and 5,435,816 (Spurgeon et al.). Other descriptions ofsuitable methods are reported in U.S. Pat. Nos. 5,437,754 (Calhoun);5,454,844 (Hibbard et al.); and 5,304,223 (Pieper et al.). Manufactureis preferably conducted in a clean environment (e.g., a class 100, class1,000, or class 10,000 clean room) to minimize any contamination in theabrasive article.

A suitable method includes preparing a slurry comprising abrasiveparticles, binder precursor and optional additives; providing aproduction tool having a front surface; introducing the slurry into thecavities of a production tool having a plurality of cavities;introducing a backing to the slurry covered surface of the productiontool; and at least partially curing or gelling the binder precursorbefore the article departs from the cavities of the production tool toform abrasive composites.

The slurry is made by combining together by any suitable mixingtechnique the binder precursor, the abrasive particles and the optionaladditives. Examples of mixing techniques include low shear and highshear mixing, with high shear mixing being preferred. Ultrasonic energymay also be utilized in combination with the mixing step to lower theslurry viscosity (the viscosity being important in the manufacture ofthe abrasive article) and/or affect the rheology of the resultingabrasive slurry. Alternatively, the slurry may be heated in the range of30 to 70° C., microfluidized or ball milled in order to mix the slurry.

Typically, the abrasive particles are gradually added into the binderprecursor. It is preferred that the slurry be a homogeneous mixture ofbinder precursor, abrasive particles and optional additives. Ifnecessary water and/or solvent is added to lower the viscosity. Theformation of air bubbles may be minimized by pulling a vacuum eitherduring or after the mixing step.

The coating station can be any conventional coating means such as dropdie coater, knife coater, curtain coater, vacuum die coater or a diecoater. The preferred coating technique is a vacuum fluid bearing diereported in U.S. Pat. Nos. 3,594,865; 4,959,265 (Wood); and 5,077,870(Millage). During coating, the formation of air bubbles is preferablyminimized although in some instances it may be preferred to incorporateair into the slurry as the slurry is being coated into the productiontool. Entrapped air may led to porosity such as voids in the abrasivecoating and possibly increase the erodibility of the abrasive composite.Additionally, a gas can be pumped into the slurry either during mixingor coating.

After the production tool is coated, the backing and the slurry arebrought into contact by any means such that the slurry wets a surface ofthe backing. The slurry is brought into contact with the backing bycontact nip roll which forces the resulting construction together. Thenip roll may be made from any material; however, the nip roll ispreferably made from a structural material such as metal, metal alloys,rubber or ceramics. The hardness of the nip roll may vary from about 30to 120 durometer, preferably about 60 to 100 durometer, and morepreferably about 90 durometer.

Next, energy is transmitted into the slurry by energy source to at leastpartially cure the binder precursor. The selection of the energy sourcewill depend in part upon the chemistry of the binder precursor, the typeof production tool as well as other processing conditions. The energysource should not appreciably degrade the production tool or backing.Partial cure of the binder precursor means that the binder precursor ispolymerized to such a state that the slurry does not flow. If needed,the binder precursor may be fully cured after it is removed from theproduction tool using conventional energy sources.

After at least partial cure of the binder precursor, the production tooland abrasive article are separated. If the binder precursor is not fullycured, the binder precursor can then be fully cured by either timeand/or exposure to an energy source. Finally, the production tool isrewound on mandrel so that the production tool can be reused again andabrasive article is wound on a second mandrel.

In another variation of this first method, the slurry is coated onto thebacking and not into the cavities of the production tool. The slurrycoated backing is then brought into contact with the production toolsuch that the slurry flows into the cavities of the production tool. Theremaining steps to make the abrasive article are the same as detailedabove.

It is preferred that the binder precursor is cured by radiation energy.The radiation energy may be transmitted through the backing or throughthe production tool. The backing or production tool should notappreciably absorb the radiation energy. Additionally, the radiationenergy source should not appreciably degrade the backing or productiontool. For instance, ultraviolet light can be transmitted through apolyester backing. Alternatively, if the production tool is made fromcertain thermoplastic materials, such as polyethylene, polypropylene,polyester, polycarbonate, poly(ether sulfone), poly(methylmethacrylate), polyurethanes, polyvinylchloride, or combinationsthereof, ultraviolet or visible light may be transmitted through theproduction tool and into the slurry. For thermoplastic based productiontools, the operating conditions for making the abrasive article shouldbe set such that excessive heat is not generated. If excessive heat isgenerated, this may distort or melt the thermoplastic tooling.

The energy source may be a source of thermal energy or of radiationenergy, such as electron beam, ultraviolet light, or visible light. Theamount of energy required depends on the chemical nature of the reactivegroups in the binder precursor, as well as upon the thickness anddensity of the binder slurry. For thermal energy, an oven temperature offrom about 50° C. to about 250° C. and a duration of from about 15minutes to about 16 hours are generally sufficient. Electron beamradiation or ionizing radiation may be used at an energy level of about0.1 to about 10 Mrad, preferably at an energy level of about 1 to about10 Mrad. Ultraviolet radiation includes radiation having a wavelengthwithin a range of about 200 to about 400 nanometers, preferably within arange of about 250 to 400 nanometers. Visible radiation includesradiation having a wavelength within a range of about 400 to about 800nanometers, preferably in a range of about 400 to about 550 nanometers.

The resulting solidified slurry or abrasive composite will have theinverse pattern of the production tool. By at least partially curing orsolidifying on the production tool, the abrasive composite has a preciseand predetermined pattern.

The production tool has a front surface which contains a plurality ofcavities or indentations. These cavities are essentially the inverseshape of the abrasive composite and are responsible for generating theshape and placement of the abrasive composites.

These cavities may have geometric shapes that are the inverse shapes ofthe abrasive composites. The dimensions of the cavities are selected toachieve the desired number of abrasive composites/square centimeter. Thecavities may be present in a dot-like pattern where adjacent cavitiesbutt up against one another at their portions where the indentationsmerge into a common substantially planar major surface of the productiontool formed in the interstices of the cavities.

The production tool may be in the form of a belt, a sheet, a continuoussheet or web, a coating roll such as a rotogravure roll, a sleevemounted on a coating roll, or die. The production tool may be made ofmetal, (e.g., nickel), metal alloys, or plastic. The production tool isfabricated by conventional techniques, including photolithography,knurling, engraving, hobbing, electroforming, or diamond turning. Forexample, a copper tool may be diamond turned and then a nickel metaltool may be electroplated off of the copper tool. Preparations ofproduction tools are reported in U.S. Pat. Nos. 5,152,917 (Pieper etal.); 5,489,235 (Gagliardi et al.); 5,454,844 (Hibbard et al.);5,435,816 (Spurgeon et al.); PCT WO 95/07797 (Hoopman et al.); and PCTWO 95/22436 (Hoopman et al.).

A thermoplastic tool may be replicated off a metal master tool. Themaster tool will have the inverse pattern desired for the productiontool. The master tool is preferably made of metal, such as nickel-platedaluminum, copper or bronze. A thermoplastic sheet material optionallymay be heated along with the master tool such that the thermoplasticmaterial is embossed with the master tool pattern by pressing the twotogether. The thermoplastic material can also be extruded or cast ontoto the master tool and then pressed. The thermoplastic material iscooled to a nonflowable state and then separated from the master tool toproduce a production tool.

Suitable thermoplastic production tools are reported in U.S. Pat. No.5,435,816 (Spurgeon et al.). Examples of thermoplastic materials usefulto form the production tool include polyesters, polypropylene,polyethylene, polyamides, polyurethanes, polycarbonates, or combinationsthereof. It is preferred that the thermoplastic production tool containadditives such as anti-oxidants and/or UV stabilizers. These additivesmay extend the useful life of the production tool. The production toolmay also contain a release coating to permit easier release of theabrasive article from the production tool. Examples of such releasecoatings include silicones and fluorochemicals.

There are many methods for making abrasive composites having irregularlyshaped abrasive composites. While being irregularly shaped, theseabrasive composites may nonetheless be set out in a predeterminedpattern, in that the location of the composites is predetermined. In onemethod, the slurry is coated into cavities of a production tool togenerate the abrasive composites. The production tool may be the sameproduction tool as described above in the case of precisely shapedcomposites. However, the slurry is removed from the production toolbefore the binder precursor is cured or solidified sufficiently for itto substantially retain its shape upon removal from the production tool.Subsequent to this, the binder precursor is cured or solidified. Sincethe binder precursor is not cured while in the cavities of theproduction tool, this typically results in the slurry flowing anddistorting the abrasive composite shape.

Methods to make this type of abrasive article are reported in U.S. Pat.Nos. 4,773,920 (Chasman et al.) and 5,014,468 (Ravipati et al.).

In a variation of this method, the slurry can be coated onto thebacking. The backing is then brought into contact with the productiontool such that the cavities of the production tool are filled by theslurry. The remaining steps to make the abrasive article are the same asdetailed above. After the abrasive article is made, it can be flexedand/or humidified prior to converting.

In another method of making irregularly shaped composites, the slurrycan be coated onto the surface of a rotogravure roll. The backing comesinto contact with the rotogravure roll and the slurry wets the backing.The rotogravure roll then imparts a pattern or texture into the slurry.Next, the slurry/backing combination is removed from the rotogravureroll and the resulting construction is exposed to conditions to solidifythe binder precursor such that an abrasive composite is formed. Avariation of this process is to coat the slurry onto the backing andbring the backing into contact with the rotogravure roll.

The rotogravure roll may impart desired patterns such as frustums ofspheres, pyramids, truncated pyramids, cones, cubes, blocks, or rods.The pattern may also be hexagonal arrays, ridges, or lattices. It isalso possible to have ridges made of geometric shapes such as prisms.The rotogravure roll may also impart a pattern such that there is a landarea between adjacent abrasive composites. This land area can comprise amixture of abrasive particles and binder. Alternatively, the rotogravureroll can impart a pattern such that the backing is exposed betweenadjacent abrasive composite shapes. Similarly, the rotogravure roll canimpart a pattern such that there is a mixture of abrasive compositeshapes.

Another method is to spray or coat the slurry through a screen togenerate a pattern and the abrasive composites. Then the binderprecursor is cured or solidified to form the abrasive composites. Thescreen can impart any desired pattern such as frustums of spheres,pyramids, truncated pyramids, cones, cubes, blocks, or rods. The patternmay also be hexagonal arrays, ridges, or lattices. It is also possibleto have ridges made of geometric shapes such as prisms. The screen mayalso impart a pattern such that there is a land area between adjacentabrasive composites. This land area can comprise a mixture of abrasiveparticles and binder. Alternatively, the screen may impart a patternsuch that the backing is exposed between adjacent abrasive composites.Similarly, the screen may impart a pattern such that there is a mixtureof abrasive composite shapes. This process is reported in U.S. Pat. No.3,605,349 (Anthon).

Another method to make a three-dimensional, textured, abrasive articleuses embossed backings. Briefly, an embossed backing is coated with aslurry. The slurry follows the contours of the embossed backing toprovide a textured coating. The slurry may be applied over the embossedbacking by any suitable technique such as roll coating, spraying, diecoating, or knife coating. After the slurry is applied over the embossedbacking, the resulting construction is exposed to an appropriate energysource to initiate the curing or polymerization process to form theabrasive composite. An example of abrasive composites on an embossedbacking is reported in U.S. Pat. No. 5,015,266 (Yamamoto et al.).

Another method of making an abrasive article using an embossed backingis reported in U.S. Pat. No. 5,219,462 (Bruxvoort). A slurry is coatedinto the recesses of an embossed backing. The slurry contains abrasiveparticles, binder precursor and an expanding agent. The resultingconstruction is exposed to conditions such that the expanding agentcauses the slurry to expand above the front surface of the backing. Nextthe binder precursor is solidified to form abrasive composites.

A variation of this embossed backing method uses a perforated backinghaving an abrasive coating bonded to the front surface of the backing.This perforated backing will have a series or a predetermined placementof holes or cavities that extend through the thickness of the backing.The slurry is coated (e.g., knife coated) over the backing. Theseslurry-filled cavities will inherently create a textured abrasivecoating. The perforated backing may optionally be removed after thecuring step if the abrasive articles are supported by an appropriatecarrier.

An alternative method of making the abrasive article uses thermoplasticbinder. The article can be prepared with or without a backing.Typically, the thermoplastic binder, abrasive particles and any optionaladditives are compounded together according to conventional techniquesto give a mixture, feeding the mixture into an extruder, and optionallyforming the mixture into pellets or long stands. The abrasive article isthen formed according to any of a variety of conventional protocols.

For example, the abrasive article may be formed by injection orcompression molding the mixture using a mold having essentially theinverse pattern of the desired pattern of the abrasive article surface.The mixture may also be heated to the point at which it forms a moltenslurry, which is then supplied to a mold and cooled. Alternatively, itis also possible to heat the binder until it flows and then add abrasiveparticles and any additives to form the molten slurry and then convertthe molten slurry into abrasive composites using conventional methods.

Objects and advantages of this disclosure are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this disclosure.

EXAMPLES Test Procedure 1

The ability of a number of abrasive articles to remove metal from awafer surface was determined by Test Procedure 1. This test proceduresimulated processing a wafer surface. The wafer surface for this testprocedure was a silicon oxide base wafer with either a copper oraluminum (10,000 Angstroms thick layer) surface.

The metal coated wafer was made from a single crystal silicon base unithaving a diameter of 100 mm and a thickness of about 0.5 mm waspurchased from either Wafernet or Silicon Valley Microelectronics, bothof San Jose, Calif. Before deposition of the metal layer, a layer ofthermal oxide (i.e., thermally grown silicon oxide) was grown on thesilicon wafer surface. This layer was approximately 5,000 Angstromsthick. In some instances, a titanium (Ti) or a titanium nitrideadhesion/barrier layer was deposited on the thermal oxide layer prior tometal deposition. The thickness of any Ti was between about 50 and 500Angstroms, and any titanium nitride was between about 100 to 3,000Angstroms. A uniform layer of either copper or aluminum was thendeposited over the silicon base using physical vapor deposition (PVD).The thickness of the metal layer was measured using a four point probe.

The test machine was a modified Strasbaugh Lapping Machine, Model 6Y-1similar to the apparatus depicted in FIG. 3. The wafer workpiece wasrested on a foam backing available from Rodel of Newark, Del., under thetrade designation “DF200”, and the assembly was placed into a springloaded plastic retaining ring. The abrasive article of the example wasadhered to a “PCF20” support pad was affixed to the platen of theStrasbaugh.

The carrier head holding the wafer was brought into contact with theabrasive article and then the wafer was rotated at about 100 rpm and theabrasive article was rotated at about 67 rpm. Both the wafer andabrasive article rotated in a clockwise manner. In addition to rotating,the wafer moved through an arc (approximately 31 mm with a nine secondperiodicity) starting about 13 mm from the edge of the abrasive article.The abrasive article and carrier head were brought into contact with oneanother at a downforce of about 350 KPa (50 pounds) unless otherwisespecified. Hydrogen peroxide solution (15% by weight H₂O₂ in deionizedwater) was pumped onto the wafer and abrasive interface at a flow rateof about 80 ml/minute. The abrasive article was used to polish the waferfor a one minute (60 second) cycle. After the polishing cycle, the waferwas removed from the holder, rinsed with deionized water and dried.

The metal removal rate was calculated by determining the change in metalfilm thickness. The initial (i.e., before polishing) and final (i.e.,after polishing) measurements were taken at the same locations using thesame four point probe. Between two and five readings were averaged todetermine the removal rate in Angstroms per minute (Å/min.).

Before polishing the metalized wafer with the abrasive article of theexamples 1-9, a wafer with a continuous layer of thermally grown siliconoxide was first polished for 1 to 4 minutes before the testing of theactual metal coated wafer. Either deionized water or hydrogen peroxidewas used as the working fluid. The silicon oxide wafers were run undersimilar conditions to those used for the metal coated test wafers.

The designations in Table 1 are used in the description of Articles1-14. TABLE 1 Material Designations Designation Material EAA A 76micrometer thick (3 mil thick) polyester film containing an ethyleneacrylic acid co-polymer primer on the front surface PVDC A 100micrometer thick (3.95 mil thick) polyester film containing anpolyvinylidene chloride prime on the front surface SR256 2(2-ethoxyethoxy) ethyl acrylate, commercially available from SartomerCo., Inc,. under the trade designation “SARTOMER SR256” SR339 2-phenoxyethyl acrylate, commercially available from Sartomer Co., Inc., underthe trade designation “Sartomer SR339” SR351 Trimethylolpropanetriacrylate (TMPTA), commercially available from Sartomer Co., Inc.,under the trade designation “Sartomer SR351” SR492 Propoxylated TMPTA,commercially available from Sartomer Co., Inc., under the tradedesignation “SARTOMER SR492” CD501 Propoxylated TMPTA, commerciallyavailable from Sartomer Co., Inc., under the trade designation “CD501”CN980 Aliphatic urethane acrylate, blended with 2-phenoxy ethylacrylate, commercially available from Sartomer Co., Inc., under thetrade designation “CN 980 M50” LR88932,4,6-trimethylbenzoyl-diphenyl-phosphine oxide liquid photoinitiator,commercially available from BASF, Charlotte, NC under the tradedesignation “LUCIRIN LR8893” FP4 A dispersing agent, commerciallyavailable from ICI America Inc., Wilmington, DE under the tradedesignations “HYPERMER PS4” and “HYPERMER FP4” D111 A dispersing agent,commercially available from Byk Chemie, Wallingford, CT under the tradedesignation “DISPERBYK 111” CEO Ceria abrasive particles having anaverage particle size of about 0.5 micrometer, commercially availablefrom Rhone Poulenc, Shelton, CT under the trade designation “PolishingOpaline” ALT Alumina trihydrate particles having an average particlesize of about 2 micrometers, commercially available from HuberEngineered Minerals, Norcross, GA under the trade designation “MICRAL932” ALA Agglomerated alpha alumina particles having an average particlesize of about 0.3 micrometer, commercially available from PraxairSurface Technologies, Indianapolis, IN under the trade designation “A”AAF Alpha alumina particles having an average particle size of about 0.3micrometer, commercially available from Praxair Surface Technologies,Indianapolis, IN under the trade designation “A-AF” A174 A3-methacryloxypropyltrimethoxysilane coupling agent, commerciallyavailable from OSI Specialties, Inc., Danbury, CT, under the tradedesignation “A-174” SR9003 Propoxylated neopentyl glycol diacrylate fromSartomer TRS2039 Mostly alpha alumina particles having an averageparticle size of about 0.2 micron, obtained from Ferro Corporation, PennYan, NY F1 617 Primed PET film obtained from ICI Corporation,Wilmington, DE OA Oleic acid, commercially available from AldrichChemical Company of Milwaukee, WI, under the designation “oleic acid,tech grade 90%” B-CEA Beta carboxyethyl acrylate, commercially availablefrom Rhome-Poulenc of Cranbury, NJ, under the trade designation “SipomerB-CEA BTA 1-H-benzotriazole, commercially available from AldrichChemical Company of Milwaukee, WI

Article 1 was prepared by combining, in order, 18.75 grams of SR492,56.25 grams of SR256, 1.5 grams of D111, and 2.4 grams of LR8893 andmixing with a high shear mixer for 1 minute. While still stirring, 100grams of ALT, which had been heated at 500° C. for 4 hours, were addedand the abrasive slurry was mixed for approximately 10 additionalminutes. This abrasive slurry was then coated onto EAA according to theGeneral Procedure for Making the Abrasive Article.

Article 2 was prepared by combining, in order, 56.27 grams of SR492,168.75 grams of SR256, 15.01 grams of D111, and 7.21 grams of LR8893 andmixing with a high shear mixer for 1 minute. While still stirring, 300grams of ALA were added and the abrasive slurry was mixed forapproximately 10 additional minutes. This abrasive slurry was thencoated onto EAA according to the General Procedure for Making theAbrasive Article.

Article 3 was prepared by combining, in order, 18.75 grams of SR351,56.25 grams of SR256, 5.83 grams of FP4, and 2.49 grams of LR8893 andmixing with a high shear mixer for 1 minute. While still stirring,400.58 grams of CEO were added and the abrasive slurry was mixed forapproximately 10 additional minutes. This abrasive slurry was thencoated onto EAA according to the General Procedure for Making theAbrasive Article.

Article 4 was prepared by combining, in order, 18.75 grams of SR351,56.28 grams of SR256, 3.26 grams of D111, and 2.40 grams of LR8893 andmixing with a high shear mixer for 1 minute. While still stirring,131.01 grams of AAF were added and the abrasive slurry was mixed forapproximately 10 additional minutes. This abrasive slurry was thencoated onto EAA according to the General Procedure for Making theAbrasive Article.

Article 5 was prepared by combining, in order, 18.76 grams of SR351,56.28 grams of SR256, 8.0 grams of D111, and 2.40 grams of LR8893 andmixing with a high shear mixer for 1 minute. While still stirring, 160grams of ALT, which had been heated at 400° C. for 4 hours, were addedand the abrasive slurry was mixed for approximately 10 additionalminutes. This abrasive slurry was then coated onto EAA according to theGeneral Procedure for Making the Abrasive Article.

Articles 1-5 were tested according to Test Procedure I. For Article 1,ten different metal test wafers (designated 1-1 to 1-10) were polishedwith the same abrasive article, and a thermal oxide wafer was polishedfor 2 minutes prior to the first metal test wafer and then between eachsuccessive metal test wafer a thermal oxide wafer was polished for 4minutes. For Article 2, a thermal oxide wafer was polished for 2 minutesprior to the metal test wafer. For Article 3, a thermal oxide wafer, ametal wafer, and a second thermal oxide wafer were polished for 1 minuteprior to the metal test wafer. For Articles 4 and 5, a thermal oxidewafer was polished for 1 minute prior to the metal test wafer. ForArticle 4, a second thermal oxide wafer and metal test wafer werepolished for 1 minute. For Article 3, the abrasive article was rotatedat about 80 rpm. Table 2 below reports the type of metal layer on thewafer, the downforce between the carrier head and the abrasive article,and the metal removal rate. TABLE 2 Article Metal Downforce (KPa (lb))Removal Rate (Å/min.) 1-1 Al 300 (43) 11283 1-2 Al 300 (43) 9000 1-3 Al300 (43) 9429 1-4 Al 300 (43) 6863 1-5 Al 300 (43) 8138 1-6 Al 300 (43)9903 1-7 Al 300 (43) 7464 1-8 Al 300 (43) 7682 1-9 Al 300 (43) 7074 1-10Al 300 (43) 8642 2 Al 300 (43) 6492 3 Cu 350 (50) 2247 4 Cu 350 (50)2013 5 Cu 350 (50) 359

The surface finish of the test wafers treated with Article 1 (wafer #5),Article 3 and the second metal test wafer with Article 4 was measuredwith a light interferometer, commercially available from WYCO Corp.,Phoenix, Ariz., under the trade designation WYCO RST PLUS. The peak tovalley range (Rt) measurements were 962 Å, 204 Å and 210 Å,respectively.

Article 6 was prepared by combining, in order, 7.50 grams of CN980,45.00 grams of SR256, 3.75 grams of SR339, 18.75 grams of SR351, 7.01grams of FP4, and 2.40 grams of LR8893 and mixing with a high shearmixer for 1 minute. While still stirring, 467.30 grams of CEO were addedand the abrasive slurry was mixed for approximately 10 additionalminutes. This abrasive slurry was then coated onto PVDC according to theGeneral Procedure for Making the Abrasive Article.

Article 7 was prepared by combining, in order, 7.50 grams of CN980,48.75 grams of SR256, 18.75 grams of SR351, 5.31 grams of D111, and 2.40grams of LR8893 and mixing with a high shear mixer for 1 minute. Whilestill stirring, 151.60 grams of AAF were added and the abrasive slurrywas mixed for approximately 10 additional minutes. This abrasive slurrywas then coated onto PVDC according to the General Procedure for Makingthe Abrasive Article.

Articles 6 and 7 were tested according to Test Procedure I on copper.For both Examples 6 and 7, a thermal oxide wafer was polished for 1minute (60 seconds) prior to the metal test wafer. Multiple test waferswere tested with each example (i.e., the same abrasive article was usedmultiple times), with two data points calculated and averaged for eachrun. Table 3 below reports the metal removal rates for the various runs.TABLE 3 Article Removal Rate (Å/min.) 6 2872 6 3004 6 2559 6 2308 6 23077 2146 7 685 7 1306

Article 8 was prepared by combining, in order, 37.51 grams of CD501,112.51 grams of SR256, 16.53 grams of D111, and 4.80 grams of LR8893 andmixing with a high shear mixer for 1 minute. While still stirring,400.00 grams of AAF were added and the abrasive slurry was mixed forapproximately 10 additional minutes. This abrasive slurry was thencoated onto PVDC according to the General Procedure for Making theAbrasive Article.

Article 9 was prepared by combining, in order, 15.02 grams of CN980,97.20 grams of SR256, 37.50 grams of SR351, 14.08 grams of FP4, and 4.80grams of LR8893 and mixing with a high shear mixer for 1 minute. Whilestill stirring, 938 grams of CEO were added and the abrasive slurry wasmixed for approximately 10 additional minutes. This abrasive slurry wasthen coated onto PVDC according to the General Procedure for Making theAbrasive Article.

The abrasive articles of Articles 8 and 9 were tested according to TestProcedure I on copper, but various working fluids were used. For allruns, a thermal oxide wafer was polished for 1 minute (60 seconds) priorto the metal test wafer using DI water as the working fluid. A newabrasive article was used for each test except in the case of Article 9with H₂O₂, which was tested using the same pad on which the nitric acidsolution was tested. Table 4 below reports the working fluids used andthe metal removal rates for the various runs. TABLE 4 Article 8 Article9 Removal Rate Removal Rate Working Fluid (Å/min.) (Å/min.) H₂O nottested 193 H₂O₂ 1007 2471 HNO₃ 1598 175 HNO₃ + Benzotriazole 569 0 NH₄OH1940 1597 NH₄OH + K₃Fe(CN)₆ 5475 5713

The various working fluid solutions were made as follows: The H₂O₂solution was made by diluting 30% hydrogen peroxide (by weight) with anequivalent weight of deionized water. The NH₄OH solution was made bycombining 10 ml of 30% ammonium hydroxide (by weight) with enoughdeionized water to make 1,000 ml total volume.

The NH₄OH/K₃Fe(CN)₆ solution was made by creating the previouslydescribed NH₄OH solution, then combining 990 g of the NH₄OH solutionwith 10 g of K₃Fe(CN)₆ and stirring until the salt was completelydissolved. The HNO₃ solution was made by combining 10 ml of 70% HNO₃ (byweight) in water with enough deionized water to make 1,000 ml totalvolume. The HNO₃/benzotriazole solution was made by creating thepreviously described HNO₃ solution, then combining 999 g of thatsolution with 1 gram of benzotriazole and stirring until thebenzotriazole was dissolved.

Test Procedure II

The copper test pattern wafer was made by initially forming about 5,000angstroms of silicon dioxide using a thermal deposition technique on thesurface of a 4 inch silicon wafer. The wafer was patterned by etching aseries of 100 micron square features to a depth of about 5,000angstroms. The pattern wafer was then coated with 200 angstroms of PVDtitanium followed by about 10,000 angstroms of PVD copper.

The test wafer was polished for a total of 7.5 minutes. A workingsolution composed of 15% hydrogen peroxide, 0.425% phosphoric acid, 0.2%benzotrizole, 8% polyethylene glycol (molecular weight 600) was appliedto the wafer during polishing. The amounts were calculated as weightpercentages. Significant areas of the wafer had copper and titaniumremoved from the surface of the wafer, exposing the silicon oxide stoplayer except in the etched 100 micron square features.

The following examples demonstrate the utility of the fixed abrasive forplanarizing a copper-deposited silicon wafer to a thermal oxide stoplayer.

Article 10 was prepared by combining, in order, 60.01 grams of SR9003,90.03 grams of SR339, 11.12 grams of D111, and 4.8 grams of LR8893 andmixing with a high shear mixer for 1 minute. While still stirring,370.01 grams of TRS2039 was added and the abrasive slurry was mixed forapproximately 10 additional minutes. This abrasive slurry was thencoated onto F1 according to the General Procedure for Making theAbrasive Article using a polypropylene production tool which containedcavities in the shape of cylinders. The cylinders were about 175 micronsin diameter and about 2.5 mils high with a bearing area ratio of about20%.

Article 10 was tested according to the Test Procedure II, and theprofile of the 100 micron square features on the wafer were measured todetermine the extent of dishing in areas on the surface which had copperremoved to expose the silicon dioxide stop layer. The Tencor P-22profilometer was used to measure the dishing. Six different sites on thewafer were measured. The measurements are reported in Table 5. TABLE 5Dishing Site (TIR, Å) 1 2957 2 1174 3 2288 4 3504 5 3271 6 2256Test Procedure III

The copper test pattern wafer was made by initially forming about 5,000Angstroms of silicon dioxide using a thermal deposition technique on thesurface of a 4 inch silicon wafer. The wafer was patterned by etching aseries of 100 micron square features to a depth of about 5,000Angstroms. The pattern wafer was then coated with 200 Angstroms of PVDtitanium followed by about 10,000 Angstroms of PVD copper.

The test wafer was polished for a total of 3.0 minutes. A workingsolution of 3.3% H₂O₂, 93.1% H₂O, 3.0% (NH₄)₂HPO₄, 0.5% (NH₄)₃ Citrateand 0.1% BTA was applied to the wafer during polishing. The amounts werecalculated as weight percentages. Significant areas of the wafer hadcopper and titanium removed from the surface of the wafer, exposing thesilicon oxide stop layer except in the etched 100 micron squarefeatures.

Article 11 was prepared by combining, in order, 30.0 grams SR9003, 45grams of SR339, 6.9 grams of “DISPERBYK 111” and 2.4 grams LR8893, andmixing with a high shear mixer for 1 minute. While stirring, 370.01grams of TRS2039 was added and the abrasive slurry was mixed forapproximately 10 additional minutes. The abrasive slurry was then coatedonto F1 according to the General Procedure for Making the AbrasiveArticle using a polypropylene production tool which contained cavitiesin the shape of cylinders or post. Article 11 was prepared using aproduction tool having 200 μm post. Article 11 was tested according toTest Procedure III and the profile of the 100 micron square features onthe wafer were measured to determine the extent of dishing in areas onthe surface which had copper removed to expose the silicon dioxide stoplayer. The Tencor P-22 profilometer was used to measure the dishing.Four different sites on the wafer were measured. The measurements arereported in Table 6. TABLE 6 Dishing Site (TIR, Å) 1 1990 2 1880 3 13904 1080

Other abrasive articles that have been prepared are described below:

Article 12 was prepared as described for Article 11, however using aproduction tool having 960 μm posts.

Article 13 was prepared as described for Article 11, however, using aproduction tool having 1,000 μm posts. The production tools aredescribed in greater detail below.

Article 14 was prepared by combining, in order, 30.0 grams SR90003, 45.0grams of SR3392, 1.53 oleic acid, 3.56 B-CEA, 2.4 grams LR8893, and144.5 grams TRS2039. The abrasive slurry was then coated onto F1according to the General Procedure for Making the Abrasive Article usinga polypropylene production tool which contained cavities in the shape ofcylinders or post. Article 14 was prepared using a tool having 200 μmposts.

Article 15 was prepared as described for Article 14, however, using aproduction tool having 960 μm posts. Typically the method of preparingan abrasive article to be used for modifying the surface of a wafersuitable for semiconductor planarization includes a filtration step.Before coating the abrasive slurry into a production tool, the abrasiveslurry is filtered through either a 60 μm or 80 μm filter.

General Procedure for Making the Abrasive Article

Abrasive articles of Articles 1-15 were made by the following procedure:

A polypropylene production tool was made by casting polypropylenematerial on a metal master tool having a casting surface comprised of acollection of adjacent truncated pyramids. The resulting production toolcontained cavities that were in the shape of truncated pyramids. Thepyramidal pattern was such that their adjacent bases were spaced apartfrom one another no more than about 510 micrometers (0.020 inch). Theheight of each truncated pyramid was about 80 micrometers, the base wasabout 178 micrometers per side and the top was about 51 micrometers perside.

The 200 micron post pattern is a triangular array of cylindrical posts,the posts having a diameter of 200 microns, a height of 60 microns, anda center to center spacing of 373 microns.

The 960 micron post pattern is a triangular array of cylindrical posts,the posts having a diameter of 960 microns, a height of 75 microns, anda center to center spacing of 1500 microns.

The 1,000 micron post pattern is a triangular array of square posts. Theposts are 1,000 microns on a side, 100 microns high, and have a centerto center spacing of 3,400 microns. The squares all have the sameorientation and are oriented with one side parallel to one of the linesconnecting the points in the triangular array.

There were about 50 lines/centimeter delineating the array ofcomposites. The production tool was secured to a metal carrier plateusing a masking type pressure sensitive adhesive tape. An abrasiveslurry, consisting of the ingredients listed in each example, was mixedusing a high shear mixer until homogenous. The abrasive slurry was thentypically filtered through a 60 μm or 80 μm filter. This abrasive slurrywas then coated into the cavities of the production tool using asqueegee and a primed polyester film backing was brought into contactwith the abrasive slurry contained in the cavities of the productiontool. The article was then passed through a bench top laboratorylaminator, commercially available from Chem Instruments, Model #001998.The article was continuously fed between the two rubber rollers at apressure between about 40-80 psi (about 275.79−551.58 kPa) and a speedsetting of approximately 2 to 7. A quartz plate was placed over thearticle. The article was cured by passing the tool together with thebacking and abrasive slurry under either two iron doped lamps,commercially available from American Ultraviolet Company or twoultraviolet (“V” bulbs), commercially available from Fusion Systems,Inc., both which operated at about 157.5 Watts/cm (400 Watts/inch). Theradiation passed through the film backing. The speed was between about10.2-13.7 meters/minute (15-45 feet/minute) and the sample was passedthrough up to two times.

To prepare the abrasive article for testing, the abrasive article waslaminated to a pressure sensitive adhesive tape, commercially availablefrom Minnesota Mining and Manufacturing Company, St. Paul, Minn. Then, a30.5 cm (12 inch) diameter circular test sample was die cut for testing.

After the planarization process is complete, the processed wafer istypically cleaned using procedures known in the art. Generally, acleaning medium is selected such that it removes the debris withoutsubstantially damaging the wafer surface. Examples of suitable cleaningmedium include tap water, distilled water, deionized water, organicsolvents, and the like. They may be used alone or in combination witheach other. If desired, they may also include soap or other additives toaid the cleaning process.

Typically, an abrasive article of the present disclosure is used toplanarize more than one semiconductor wafer. It is within the scope ofthis disclosure that the abrasive article can be dressed or conditionedin between two consecutive planarization steps. The conditioning stepcan remove “worn abrasive particles” and/or to remove any undesirabledeposits or debris, and thereby enhance the cutting ability of theabrasive article, as well as the quality of the planarized surface. Insuch circumstances, the surface of the abrasive article may beconditioned according to well-known, conventional techniques, includingcontacting the abrasive surface with a diamond conditioning tool, brush,bonded abrasive, coated abrasive, metal rod, water jet, or the like.Other techniques include exposure to a laser or to corona energy (e.g.,using a Sherman corona treating unit available from Sherman Treaters,Ltd., United Kingdom). This conditioning step is not always preferreddue to the time and money associated with the conditioning step. It iswithin the scope of this disclosure that the abrasive is not dressed orconditioned in between two consecutive planarization steps.

Evaluation of Working Liquids

A series of experiments was carried out to evaluate various workingliquids useful in modifying a surface of a wafer suited for fabricationof a semiconductor device. In one exemplary embodiment, the workingliquids were aqueous solutions of initial components substantially freeof loose abrasive particles, the components comprising water, asurfactant, and a pH buffer exhibiting at least one pK_(a) greater than7, the pH buffer comprising a basic pH adjusting agent and an acidiccomplexing agent, and the working liquid exhibiting a pH from about 7 toabout 12. The surfactant-containing working liquids were evaluated fortheir ability to accelerate or maintain the oxide removal rate in astop-on-nitride CMP process using a fixed abrasive web.

A Reflexion™ web polisher (Applied Materials, Inc., Santa Clara, Calif.)was used to polish 200 mm Blanket TEOS wafers on a 200 mm Profiler IIwafer carrier using a 3M SWR550-125/10 fixed abrasive web (3M Company,St. Paul, Minn.) mounted on a 60/90 ribbed subpad (3M Company, St. Paul,Minn.). Surfactant-containing working liquids were prepared in deionizedwater with 0.1% w/w of a selected surfactant in a buffered aqueoussolution of ammonium hydroxide (as a basic pH control agent) and 2.5%w/w L-proline (as an acidic multidentate complexing agent). Forcomparison purposes, a control working liquid was also preparedcomprising only a buffered aqueous solution of ammonium hydroxide (as abasic pH control agent) and 2.5% w/w L-proline (as an acidicmultidentate complexing agent). The working liquids were individuallyapplied to the wafer surface during the CMP process at a volumetricflowrate of 100 mL/min.

The evaluated surfactants are listed in Table 7. The surfactants werecombined with water, a basic pH adjusting agent (e.g. ammoniumhydroxide) and a multidentate amino acid complexing agent (e.g. 2.5%w/w/L-proline) over a pH range from about 9 to 12. The working liquidswere then applied in combination with 3M's microreplicated fixedabrasive products to carry out a CMP process useful in use insemiconductor device manufacturing. TABLE 7 Surfactant DesignationsHydrophile- Critical Lipophile Micelle Surfactant Surfactant BalanceConcentration Name Type Source (HLB) (ppm) Envirogem Alkane Air Products& 4 — AD01 di-alcohol Chemicals, Inc., Allentown, PA Surfynol 61Acetylenic Air Products & — — primary alcohol Chemicals, Inc.,Allentown, PA Surfynol Acetylenic Air Products & 4 — 420 di-alcoholethoxylate Chemicals, Inc., Allentown, PA Dynol 604 Acetylenic AirProducts & — — di-alcohol ethoxylate Chemicals, Inc., Allentown, PADynol 607 Acetylenic Air Products & 8 — di-alcohol ethoxylate Chemicals,Inc., Allentown, PA Triton Secondary alcohol Dow Chemical 9.8 — X-45ethoxylate Co., Midland, MI Tergitol Secondary alcohol Dow Chemical 12.4— 15-S-7 ethoxylate Co., Midland, MI Tergitol Secondary alcohol DowChemical 12.6 33 Minfoam ethoxylate Co., 1X Midland, MI TergitolSecondary alcohol Dow Chemical 14.1 830 TMN- ethoxylate Co., 100XMidland, MI Tergitol Secondary alcohol Dow Chemical 14-15 0.7 XHethoxylate Co., Midland, MI NCW-1001 Secondary alcohol Wako Chemical —100 ethoxylate Co., Richmond, VA NCW-1002 Secondary alcohol WakoChemical — 600 ethoxylate Co., Richmond, VA L-19909 Fluorochemical 3MCo., 12 350 surfactant, a solution of St. Paul, MN 85-95% w/wfluoroaliphatic polymeric esters and 5- 10% w/w polyether polymer in <2%1- methyl-2- pyrrolidinone/toluene/2- propenoic acid blend

Specific advantages that may result at alkaline pH include the use oflower polishing pressures while maintaining adequate oxide removalrates. Generally lower polishing pressures result in reduced defects andimproved yields. The polishing process parameters included a 5 mmincrement, a 3 psi (about 20.68 kPa) wafer pressure, a plate rotationalspeed of 30 revolutions per minute (RPM), a carrier rotational speed on28 RPM, and a polishing time of 60 seconds per wafer. The results of theCMP evaluations of the surfactant-containing working liquids and thecontrol working liquids are shown in Table 8. TABLE 8 Oxide NitrideSurfactant Removal Removal Surfactant Concentration Rate Rate Name (%w/w) pH (Å/min.) (Å/min.) Control 0.0 10.5 322 — Envirogem AD01 0.0510.5 686 — Surfynol 61 0.05 10.5 842 0 Surfynol 420 0.05 10.5 636 —Dynol 604 0.05 10.5 777 1 Dynol 607 0.05 10.5 875 1 Triton X-45 0.0510.5 866 1 Tergitol 15-S-7 0.05 10.5 1,336 5 Tergitol Minfoam 1X 0.0510.5 773 — Tergitol TMN-100X 0.05 10.5 679 — Tergitol XH 0.05 10.5 681 —NCW-1001 0.05 10.5 1,065 0 NCW-1002 0.05 10.5 917 0 Control 0.05 7.0 68— Dynol 607 0.05 7.0 260 — Tergitol 15-S-7 0.05 7.0 236 — Tergitol X-450.05 7.0 189 — NCW-1001 0.05 7.0 176 —

As shown in Table 8, use of surfactants in conjunction with 2.5% w/wL-proline at a pH from 7 to 12 yielded greater than a two times increasein oxide removal rate relative to the control working liquid withoutsurfactant at similar pH. In certain examples where the pH is betweenabout 9 and 11, the oxide removal rate exceeds the nitride removal rateby a factor of 200 or more, thereby permitting stop on nitrideselectivity when the working fluid is used in a CMP STI method.

Another series of experiments was carried out to evaluate the use ofsurfactant to accelerate the break-in period for a fixed abrasive webused in CMP. A Reflexion™ web polisher (Applied Materials, Santa Clara,Calif.) was used to polish a 200 mm Blanket TEOS wafer on a 200 mmProfiler II wafer carrier (3M Company, St. Paul, Minn.) using a 3MSWR550-125/10 fixed abrasive web (3M Company, St. Paul, Minn.) mountedon a 60/90 ribbed subpad. A working liquid comprising 2.5% w/w L-Prolinein deionized water with 0.05% w/w Tergitol™ 15-S-7 surfactant (DowChemical Company, Midland, Mich.) was used at a volumetric flowrate of100 mL/min. The polishing process parameters included a 5 mm increment,a 3 psi (about 20.68 kPa) wafer pressure, a plate rotational speed of 30revolutions per minute (RPM), a carrier rotational speed on 28 RPM, anda polishing time of 60 seconds per wafer.

Three different fixed abrasive break-in procedures were used. The numberof wafers needed to reach a stable oxide removal rate at a target valueof 2000-2500 Å/min. was determined. FIG. 8 shows the polishing rate as afunction of the number of wafers processed for each break-in procedureevaluated in this experiment.

In the first test (illustrated by the diamond symbol in FIG. 8), 145wafers were processed in order to obtain a constant (stable within+/−200 Å/min.) polishing rate at the target of 2000-2500 Å/min hadreached an equilibrium state. Prior to this test, a standard wet idlehad been run overnight (about 15 hours of idle time) with the fixedabrasive web in only deionized water. The polishing rate did notcompletely stabilize at the target 2000-2500 Å/min. rate until all 140wafers had been run. This represents an excessively long break-in periodto achieve a stable polishing rate. The second test (illustrated by thesquare symbol in FIG. 8) was run after a 5 hour wet idle. In the secondtest, about 40 wafers were required to be processed in order to bringthe polishing rate to a stable target polishing rate of 2000-2500 Å/min.This is still an undesirably long break-in period. The third test(illustrated by the triangle symbol in FIG. 8) was run after the fixedabrasive web was soaked with the surfactant-containing working liquidand allowed to dry on the web overnight at room temperature. No rinsingof the fixed abrasive web was performed during the idle time prior tothe polishing. Here, the polishing rate reached a stable value at thetarget 2000-2500 Å/min rate after processing only about 25 wafers.

Other methods for keeping the surfactant on the fixed abrasive could beused as well. One example would be, rather than pumping straightdeionized water onto the web during wet idle, to use thesurfactant-containing working liquid. Another example could be the useof the surfactant alone, or the surfactant diluted into deionized waterand pumped onto the fixed abrasive web polishing surface during idletimes. Another method could use a concentrated solution of thesurfactant applied to the fixed abrasive surface just after an idleperiod.

It is apparent to those skilled in the art from the above descriptionthat various modifications can be made without departing from the scopeand principles of this disclosure, and it should be understood that thisdisclosure is not to be unduly limited to the illustrative embodimentsset forth hereinabove. Various embodiments of the disclosure have beendescribed. These and other embodiments are within the scope of thefollowing claims.

1. A working liquid useful in modifying a surface of a wafer suited forfabrication of a semiconductor device, the liquid being an aqueoussolution of initial components substantially free of loose abrasiveparticles, the components comprising: a. water; b. a pH bufferexhibiting at least one pK_(a) greater than 7, wherein the pH buffercomprises a basic pH adjusting agent and an acidic complexing agent; andc. a surfactant; wherein the working liquid exhibits a pH from about 7to about
 12. 2. A working liquid of claim 1, wherein the basic pHadjusting agent is selected from the group consisting of alkali metalhydroxides, alkaline earth metal hydroxides, ammonium hydroxide, andmixtures thereof.
 3. A working liquid of claim 1, wherein the acidiccomplexing agent comprises a multidentate acidic complexing agent. 4.The working liquid of claim 3 wherein the multidentate acidic complexingagent comprises at least one of an amino acid or a dipeptide formed froman amino acid.
 5. The working liquid of claim 4, wherein the amino acidis selected from alanine, proline, glycine, histidine, lysine, arginine,ornithene, cysteine, tyrosine, and combinations thereof.
 6. The workingliquid of claim 5, wherein the amino acid is L-proline.
 7. The workingliquid of claim 1, wherein the surfactant is a nonionic surfactant. 8.The working liquid of claim 7, wherein the nonionic surfactant exhibitsa hydrophile-lipophile balance of at least about
 10. 9. The workingliquid of claim 7, wherein the nonionic surfactant is selected from alinear primary alcohol ethoxylate, a secondary alcohol ethoxylate, abranched secondary alcohol ethoxylate, an octylphenol ethoxylate, anacetylenic primary alcohol ethoxylate, an acetylenic primary di-alcoholethoxylate, an alkane di-alcohol, a hydroxyl-terminated ethyleneoxide-propylene oxide random copolymer, a fluoroaliphatic polymericester, and mixtures thereof.
 10. The working liquid of claim 7, whereinthe nonionic surfactant is present in an amount of at least about 0.025%and at most about 0.2% by weight of the working liquid.
 11. The workingliquid of claim 1, wherein the acidic complexing agent is present in anamount from about 0.1% by weight to about 5% by weight of the workingliquid.
 12. The working liquid of claim 1, wherein the basic pHadjusting agent is present in an amount sufficient to produce a pH fromabout 10 to about 11, the acidic complexing agent comprises L-proline inan amount from about 2% to about 4% by weight of the working liquid, andthe surfactant comprises an ethoxylated alcohol in an amount from about0.05% to about 0.5% by weight of the working liquid.
 13. The workingliquid of claim 1, wherein the working liquid exhibits a pH from about 9to about
 11. 14. A method of modifying a surface of a wafer suited forfabrication of a semiconductor device comprising the steps of: a.providing a wafer comprising at least a first material having a surfaceetched to form a pattern, a second material deployed over at least aportion of the surface of the first material, and a third materialdeployed over at least a portion of the surface of the second material;b. contacting the third material of the wafer, in the presence of aworking liquid according to claim 1, with a plurality ofthree-dimensional abrasive composites fixed to an abrasive article, thethree-dimensional abrasive composites comprising a plurality of abrasiveparticles fixed and dispersed in a binder; and c. relatively moving thewafer while the third material is in contact with the plurality ofabrasive composites until an exposed surface of the wafer issubstantially planar and comprises at least one area of exposed thirdmaterial and one area of exposed second material.
 15. A method ofmodifying a surface of a wafer suited for fabrication of a semiconductordevice, comprising: a. providing a wafer comprising at least a barriermaterial deployed over at least a portion of the wafer; and a dielectricmaterial deployed over at least a portion of the barrier material; b.contacting the dielectric material of the wafer, in the presence of aworking liquid according to claim 1, with a plurality ofthree-dimensional abrasive composites fixed to an abrasive article, thethree-dimensional abrasive composites comprising a plurality of abrasiveparticles fixed and dispersed in a binder; and c. relatively moving thewafer while the dielectric material is in contact with the plurality ofabrasive composites until an exposed surface of the wafer issubstantially planar and comprises at least one area of exposeddielectric material and one area of exposed barrier material.
 16. Themethod of claim 15, wherein the barrier material comprises siliconnitride, and the dielectric material comprises silicon oxide.
 17. Afixed abrasive article comprising: a plurality of three-dimensionalabrasive composites fixed to an abrasive article, the three-dimensionalabrasive composites comprising a plurality of abrasive particles fixedand dispersed in a binder; and a surfactant disposed on at least aportion of a surface of the three-dimensional abrasive composites. 18.The fixed abrasive article of claim 17, wherein the surfactant comprisesa nonionic surfactant.
 19. The fixed abrasive article of claim 18,wherein the nonionic surfactant is a water soluble surfactant.
 20. Thefixed abrasive article of claim 19, wherein the nonionic water solublesurfactant exhibits a hydrophile-lipophile balance of at least about 10.21. The fixed abrasive article of claim 20, wherein the nonionic watersoluble surfactant is selected from a linear primary alcohol ethoxylate,a secondary alcohol ethoxylate, a branched secondary alcohol ethoxylate,an octylphenol ethoxylate, an acetylenic primary alcohol ethoxylate, anacetylenic primary di-alcohol ethoxylate, an alkane di-alcohol, ahydroxyl-terminated ethylene oxide-propylene oxide random copolymer, afluoroaliphatic polymeric ester, and mixtures thereof.
 22. A method ofpreparing a fixed abrasive article for use in modifying a surface of awafer in a chemical mechanical polishing process, comprising: a.providing a fixed abrasive article having a surface comprising aplurality of three-dimensional abrasive composites fixed to an abrasivearticle, the three-dimensional abrasive composites comprising aplurality of abrasive particles fixed and dispersed in a binder; b.exposing the surface to a surfactant solution in a solvent; and c.drying the fixed abrasive article to remove at least a portion of thesolvent, thereby forming a coating of surfactant on at least a portionof the surface; optionally wherein steps (a)-(c) are repeated until atarget polishing rate is obtained and a polishing rate thereafterremains within about 200 Å/min of the target polishing rate when thefixed abrasive article is used to polish a plurality of wafer surfaces.23. The method of claim 22, wherein the surfactant comprises a nonionicsurfactant.
 24. The method of claim 23, wherein the nonionic surfactantcomprises a water soluble surfactant, and the solvent comprises water.25. The method of claim 24, wherein the nonionic water solublesurfactant exhibits a hydrophile-lipophile balance of at least about 10.26. The method of claim 23, wherein the surfactant is selected from alinear primary alcohol ethoxylate, a secondary alcohol ethoxylate, abranched secondary alcohol ethoxylate, an octylphenol ethoxylate, anacetylenic primary alcohol ethoxylate, an acetylenic primary di-alcoholethoxylate, an alkane di-alcohol, a hydroxyl-terminated ethyleneoxide-propylene oxide random copolymer, a fluoroaliphatic polymericester, and mixtures thereof.
 27. The method of claim 22, wherein thesurfactant is present in an amount of at least about 0.025% and at mostabout 5% by weight of the surfactant solution.
 28. A working liquiduseful in modifying a surface of a wafer suited for fabrication of asemiconductor device, the liquid being an aqueous solution of initialcomponents substantially free of loose abrasive particles, thecomponents comprising: a. an oxidizing agent; b. a complexing agent; c.a passivating agent comprising a material selected from the groupconsisting of benzotriazole, azole derivatives of benzotriazole, andtolytriazole; and d. a buffer comprising a polyprotic protolyte havingat least one pK_(a) greater than
 7. 29. The working liquid of claim 28wherein the buffer comprises a material selected from the groupconsisting of systems of fully or partially neutralized polyproticacids, phosphoric acid-ammonium phosphate systems, polyphosphoricacid-ammonium polyphosphate systems, boric acid-ammonium tetraboratesystems, boric acid-ammonium pentaborate systems, ion buffer systems ofaspartic acid, ion buffer systems of glutamic acid, ion buffer systemsof histidine, ion buffer systems of lysine, ion buffer systems ofarginine, ion buffer systems of ornithine, ion buffer systems ofcysteine, ion buffer systems of tyrosine, ion buffer systems ofcarnosine and combinations thereof.
 30. The working liquid of claim 28wherein the complexing agent is a multidentate complexing agent.
 31. Theworking liquid of claim 30, wherein the multidentate complexing agentcomprises a material selected from the group consisting ofpolyphosphates, 1,3-diketones, aminoalcohols, aromatic heterocyclicbases, phenols, aminophenols, oximes, Schiff bases, sulfur compounds,multidentate amines, ethylenediamine, diethylene-triamine,triethylenetetramine, multidentate carboxylic acid, citric acid,tartaric acid, oxalic acid, gluconic acid, nitriloacetic acid, aminoacids, glycine, common analytical chelating agents,ethylenediaminetetraacetic acid, and combinations thereof.
 32. Theworking liquid of claim 28 wherein the oxidizing agent comprises amaterial selected from the group consisting of hydrogen peroxide, nitricacid, sulfuric acid, chromic-sulfuric acids, coordination compounds,halogen oxo acids, salts of halogen oxo acids, ammonium persulfates,sodium persulfates, potassium persulfates and combinations thereof. 33.The working liquid of claim 32 wherein the halogen oxo acid comprises amaterial selected from a group consisting of chloric acid, chlorousacid, hypochlorous acid, bromic acid, perbromic acid, iodic acid,periodic acid, orthoperiodic acid and combinations thereof.
 34. Theworking liquid of claim 32 wherein the salt of halogen oxo acidscomprises a material selected from a group consisting of sodiumchlorate, sodium chlorite, sodium hypochlorite, sodium bromite, sodiumbromate, sodium perbromate, sodium iodates, sodium periodates, sodiumorthoperiodates and combinations thereof.
 35. The working liquid ofclaim 28 wherein the coordination compound comprises a material selectedfrom the group consisting of potassium ferricyanide, ferricyanide,ferric nitrate, ferric chloride, ammonium ferricethylenediaminetetraacetic acid, ammonium ferric citrate, ferriccitrate, ammonium ferric oxalate, cupric citrate, cupric oxalate, cupricgluconate, cupric glycinate, cupric tartrate, cupric chloride, vanadiumcoordination compounds, chromium coordination compounds, manganesecoordination compounds, cobalt coordination compounds, molybdenumcoordination compounds, tungsten coordination compounds and combinationsthereof.
 36. The working liquid of claim 28 wherein the complexing agentcomprises a material selected from the group consisting of carboxylicacid, ammonia, amines, halides, pseudohalides, carboxylates, thiolates,and combinations thereof.
 37. The working liquid of claim 28 wherein theworking liquid comprises less than 0.1% by weight of loose abrasiveparticles.
 38. The working liquid of claim 28 wherein the working liquidcomprises 0% by weight of loose abrasive particles.
 39. The workingliquid of claim 28 further comprising an additive selected from thegroup consisting of surfactants, wetting agents, reducing agents, rustinhibitors, lubricants, soaps, and combinations thereof.
 40. The workingliquid of claim 28 wherein the oxidizing agent is concentrated inaqueous solution from about 0.01% by weight to about 50% by weight. 41.The working liquid of claim 40 wherein the oxidizing agent isconcentrated in aqueous solution from about 0.02% by weight to about 40%by weight.
 42. The working liquid of claim 28 wherein the complexingagent is concentrated in aqueous solution from about 0.01% by weight toabout 50% by weight.
 43. The working liquid of claim 42 wherein thecomplexing agent is concentrated in aqueous solution from about 0.02% byweight to about 40% by weight.
 44. A working liquid useful in modifyinga surface of a wafer suited for fabrication of a semiconductor device,the liquid being an aqueous solution of initial components substantiallyfree of loose abrasive particles, the components comprising: a. anoxidizing agent; b. a complexing agent; c. a passivating agentcomprising a material selected from the group consisting ofbenzotriazole, azole derivatives of benzotriazole, and tolytriazole; andd. a buffer comprising a polyprotic protolyte having at least one pK_(a)greater than 7, wherein the oxidizing agent comprises a materialselected from the group consisting of nitric acid, sulfuric acid,chromic-sulfuric acids, coordination compounds, halogen oxo acids, saltsof halogen oxo acids, ammonium persulfates, sodium persulfates,potassium persulfates and combinations thereof.
 45. The working liquidof claim 44 wherein the complexing agent comprises a material selectedfrom the group consisting of carboxylic acid, ammonia, amines, halides,pseudohalides, carboxylates, thiolates, multidentate complexing agents,and combinations thereof.
 46. The working liquid of claim 45, whereinthe multidentate complexing agent comprises a material selected from thegroup consisting of polyphosphates, 1,3-diketones, aminoalcohols,aromatic heterocyclic bases, phenols, aminophenols, oximes, Schiffbases, sulfur compounds, multidentate amines, ethylenediamine,diethylene-triamine, triethylenetetramine, multidentate carboxylic acid,citric acid, tartaric acid, oxalic acid, gluconic acid, nitriloaceticacid, amino acids, glycine, common analytical chelating agents,ethylenediaminetetraacetic acid, and combinations thereof.
 47. A workingliquid useful in modifying a surface of a wafer suited for fabricationof a semiconductor device, the liquid being an aqueous solution ofinitial components substantially free of loose abrasive particles, thecomponents comprising: a. an oxidizing agent; b. a complexing agent; c.a passivating agent comprising a material selected from the groupconsisting of benzotriazole, azole derivatives of benzotriazole, andtolytriazole; and d. a buffer comprising a polyprotic protolyte havingat least one pK_(a) greater than 7, wherein the passivating agentcomprises a material selected form the group consisting of tolytriazole,cuprous oxide, phosphates, alkene oxide condensation products of fattyacid polyamides, 4-alkylpyrocatechols, amine borates,β-(o-carboxybenzylthio) propionitrile, chromate ion, cobalt lineolate,dicyclohexylammonium nitrite, egg albumin, formaldehyde,2-guanidinobenzimidazole, hexamethyleneamine nitrobenzoates, hydrazine,mercaptobenzothiazole, naphthenic acids, organosilicon compounds,propargyl alcohol, sodium adipate, sodium arsenite, sodium benzoate,sodium nitrite, sodium oleate, sodium sulfite, high molecular weightsulfur compounds, triethanolamine phosphate, Na₆P₄O₁₃, and combinationsthereof.
 48. The working liquid of claim 47 wherein the complexing agentcomprises a material selected from the group consisting of carboxylicacid, ammonia, amines, halides, pseudohalides, carboxylates, thiolates,multidentate complexing agents, and combinations thereof.
 49. Theworking liquid of claim 48, wherein the multidentate complexing agentcomprises a material selected from the group consisting ofpolyphosphates, 1,3-diketones, aminoalcohols, aromatic heterocyclicbases, phenols, aminophenols, oximes, Schiff bases, sulfur compounds,multidentate amines, ethylenediamine, diethylene-triamine,triethylenetetramine, multidentate carboxylic acid, citric acid,tartaric acid, oxalic acid, gluconic acid, nitriloacetic acid, aminoacids, glycine, common analytical chelating agents,ethylenediaminetetraacetic acid, and combinations thereof.